Semiconductor device, fabrication method for a semiconductor device and electronic apparatus

ABSTRACT

Disclosed herein is a semiconductor device, including: a first substrate including a first electrode, and a first insulating film configured from a diffusion preventing material for the first electrode and covering a periphery of the first electrode, the first electrode and the first insulating film cooperating with each other to configure a bonding face; and a second substrate bonded to and provided on the first substrate and including a second electrode joined to the first electrode, and a second insulating film configured from a diffusion preventing material for the second electrode and covering a periphery of the second electrode, the second electrode and the second insulating film cooperating with each other to configure a bonding face to the first substrate.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a division of U.S. patent application Ser.No. 13/533,526, filed Jun. 26, 2012, which claims priority to JapanesePatent Application Serial No. JP 2011-148883, JP 2011-168021, JP2011-170666, JP 2011-210142 and JP 2012-006356, filed in the JapanPatent Office on Jul. 5, 2011, Aug. 1, 2011, Aug. 4, 2011, Sep. 27, 2011and Jan. 16, 2012, respectively, the entire disclosures of which arehereby incorporated herein by reference.

BACKGROUND

This technology relates to a semiconductor device wherein a plurality ofsubstrates are bonded to each other to carry out joining betweenelectrodes or wiring lines, a fabrication method for the semiconductordevice and an electronic apparatus including the semiconductor device.

A technique of bonding two wafers or substrates to each other to joinjoining electrodes formed on the semiconductor substrates to each otherhas been developed already and is disclosed, for example, in JapanesePatent Laid-Open No. 2000-299379.

Further, as one of structures for achieving higher integration ofsemiconductor devices, a three-dimensional structure wherein twosubstrates on which elements and wiring lines are formed are laminatedand bonded to each other has been proposed. When a semiconductor deviceof such a three-dimensional structure as just described is to befabricated, two substrates on which elements are formed are preparedfirst, and the electrodes for joining, that is, bonding pads, are ledout to the bonding face side of the substrates. Thereupon, for example,an embedded wiring technique called damascene technique is applied toform a bonding face configured such that the electrodes for joining madeof copper (Cu) are surrounded by an insulating film. Thereafter, the twosubstrates are disposed with the bonding faces thereof opposed to eachother and then are laminated such that the electrodes provided on thebonding faces thereof correspond to each other, and in this state, heattreatment is carried out. Bonding of the substrates between which theelectrodes are joined together is carried out thereby. For thefabrication method described, refer to, for example, Japanese PatentLaid-Open No. 2006-191081 (hereinafter referred to as Patent Document1).

Formation of electrodes by a general embedded wiring technique iscarried out, for example, in the following manner. First, a groovepattern is formed on an insulating film which covers the surface of asubstrate, and then a conductive base layer or barrier metal layerhaving a barrier property with respect to copper (Cu) is formed on theinsulating film in such a state that it covers an inner wall of thegroove pattern. Then, an electrode film for which copper (Cu) is used isformed on the barrier metal layer in such a state that the groovepattern is filled up, and then the electrode film is polished until thebarrier metal layer is exposed. Further, the barrier metal layer and theelectrode film are polished until the insulating film is exposed.Consequently, an embedded electrode wherein an electrode film isembedded in the groove pattern formed in the insulating film with thebarrier metal layer interposed therebetween is formed.

With the foregoing embedded wiring technique, polishing of the electrodefilm can be stopped automatically at a point of time at which theelectrode film is polished until the barrier metal layer is exposed.However, in polishing of the electrode film and the barrier metal layerwhich is carried out subsequently, the polishing of the electrode filmcannot be stopped automatically at a point of time at which theinsulating film is exposed. Therefore, in a polishing face, dishingwherein the electrode film in the groove pattern is polished excessivelyor erosion wherein the electrode film in the groove pattern is polishedexcessively depending upon an electrode layout are liable to occur, andit is difficult to obtain a flat polished face. Therefore, a methodwherein, before the electrode film is formed, the barrier metal layer onthe insulating film is removed such that the barrier metal layer remainsonly on the inner face of the groove pattern and then an electrode filmis formed on the remaining barrier metal layer and then polished. Themethod is disclosed, for example, in Japanese Patent Laid-Open No.2000-12540 (hereinafter referred to as Patent Document 2).

SUMMARY

Incidentally, for a semiconductor device of a three-dimensionalstructure obtained by such bonding as described above, a structure isdemanded wherein bonding strength of two substrates and joining strengthbetween electrodes are assured while diffusion of an electrode materialinto an insulating film is prevented. However, the fabrication methodfor a semiconductor device disclosed in Patent Document 1 fails toprevent diffusion of an electrode material into an insulating film.

On the other hand, with the embedded wiring technique disclosed inPatent Document 2, since an electrode film is provided with a barriermetal layer or base layer, diffusion of an electrode material into anelectrode film can be prevented. However, this embedded wiring techniquedoes not take bonding of substrates into consideration, and the barriermetal layer is placed into a state in which it is exposed to a flattenedface obtained by polishing together with the electrode and theinsulating film. Therefore, it is difficult to assure sufficient bondingstrength over the overall area of the flattened face.

Therefore, it is desirable to provide a semiconductor device of athree-dimensional structure wherein, in a structure wherein joining ofelectrodes to each other is carried out by bonding of two substrates toeach other, bonding strength is assured while diffusion of an electrodematerial into an insulating material is prevented thereby to achieveenhancement of the reliability. Also it is desirable to provide afabrication method for such a semiconductor device as just described andan electronic apparatus including the semiconductor device.

According to a first embodiment of the present technology, there isprovided a semiconductor device including a first substrate including afirst electrode and a first insulating film configured from a diffusionpreventing material for the first electrode and covering a periphery ofthe first electrode, the first electrode and the first insulating filmcooperating with each other to configure a bonding face, and a secondsubstrate bonded to and provided on the first substrate and including asecond electrode joined to the first electrode and a second insulatingfilm configured from a diffusion preventing material for the secondelectrode and covering a periphery of the second electrode, the secondelectrode and the second insulating film cooperating with each other toconfigure a bonding face to the first substrate.

According to the first embodiment of the present technology, thesemiconductor device can be fabricated by a fabrication method for asemiconductor device including forming an insulating film configuredfrom a diffusion preventing material for an electrode material on eachof two substrates and forming a groove pattern on the insulating film,forming an electrode film configured from the electrode material in astate in which the electrode film fills up the groove pattern formed onthe insulating film on the insulating film of each of the substrates,polishing the electrode film of each of the substrates until theinsulating film is exposed to form a pattern of an electrode such thatthe electrode film is embedded in the groove pattern, and bonding thetwo substrates, on each of which the electrode is formed, in a state inwhich the electrodes are joined together.

With the semiconductor device and the fabrication method, in theconfiguration wherein joining of electrodes to each other is carried outby bonding of two substrates, bonding strength is assured whilediffusion of an electrode material is prevented. Consequently, thesemiconductor device of the three-dimensional structure can achieveenhancement of reliability.

According to a second embodiment of the present technology, there isprovided a semiconductor device including a first substrate having abonding face to which a first electrode and a first insulating film areexposed, an insulating thin film configured to cover the bonding face ofthe first substrate, and a second substrate having a bonding face towhich a second electrode and a second insulating film are exposed andbonded to the first substrate in a state in which the insulating thinfilm is sandwiched between the bonding face of the second substrate andthe bonding face of the first substrate and the first electrode and thesecond electrode are electrically connected to each other through theinsulating thin film.

According to the second embodiment of the present technology, thesemiconductor device can be fabricated by a fabrication method for asemiconductor device including preparing two substrates each having abonding face to which an electrode and an insulating film are exposed,forming an insulating thin film in a state in which the insulating thinfilm covers the bonding face of at least one of the two substrates, anddisposing the two substrates such that the bonding faces thereof areopposed to each other across the insulating thin film, positioning thetwo substrates in a state in which the electrodes thereof areelectrically connected to each other through the insulating thin filmand bonding the two substrates in the positioned state.

In the semiconductor device (electronic apparatus) and the fabricationmethod therefor of the present disclosure, the area of the joining sidesurface of the second metal film which is joined to the first metal filmis made smaller than the area of the joining side surface of the firstmetal film. Further, in the portion of the face region of the firstmetal film on the joining interface side which includes the face regionin which the first metal film is not joined to the second metal film,the interface barrier film is provided. With the configuration justdescribed, degradation of an electric characteristic at the joininginterface can be suppressed further, by which the joining interface isprovided with further higher reliability.

According to a third embodiment of the present technology, there isprovided a semiconductor device including a first semiconductor portionhaving a first metal film formed on the surface thereof on a joininginterface side, a second semiconductor portion having a second metalfilm joined to the first metal film on the joining interface and havinga surface area on the joining interface side smaller than a surface areaof the first metal film on the joining interface side and provided in astate in which the second semiconductor portion is bonded to the firstsemiconductor portion on the joining interface, and an interface barrierportion provided in a portion of a face region of the first metal filmon the joining interface side which includes a face region in which thefirst metal film is not joined to the second metal film.

According to the third embodiment of the present technology, there isfurther provided an electronic apparatus including a semiconductordevice including a first semiconductor portion having a first metal filmformed on the surface thereof on a joining interface side, a secondsemiconductor portion having a second metal film joined to the firstmetal film on the joining interface and having a surface area on thejoining interface side smaller than a surface area of the first metalfilm on the joining interface side and provided in a state in which thesecond semiconductor portion is bonded to the first conductor portion onthe joining interface, and an interface barrier portion provided in aportion of a face region of the first metal film on the joininginterface side which includes a face region in which the first metalfilm is not joined to the second metal film, and a signal processingcircuit configured to process an output signal of the semiconductordevice.

According to the third embodiment of the present technology, thesemiconductor device can be fabricated by a fabrication method for asemiconductor device including producing a first semiconductor portionhaving a first metal film formed on a surface thereof on a joininginterface side, producing a second semiconductor portion having a secondmetal film having a surface area on the joining interface side smallerthan a surface area of the first metal film on the joining interfaceside, and bonding the surface of the first semiconductor portion on thefirst metal film side and the surface of the second semiconductorportion on the second metal film side to each other to join the firstmetal film and the second metal film to each other and providing aninterface barrier portion at a portion of the face region of the firstmetal film on the joining interface side which includes the face regionin which the first metal film is not joined to the second metal film.

According to a fourth embodiment of the present technology, there isprovided a semiconductor device including a semiconductor substrate, aninsulating layer formed on the semiconductor substrate, a joiningelectrode formed on a surface of the insulating layer, and a protectivelayer formed on a surface of the insulating layer and surrounding thejoining electrode with the insulating layer interposed therebetween.

According to the fourth embodiment of the present technology, thesemiconductor device can be fabricated by a fabrication method for asemiconductor device including forming an insulating layer on asemiconductor substrate, forming a joining electrode on a surface of theinsulating layer, and forming a protective layer at a position of thesurface of the insulating layer at which the protective layer surroundsthe joining electrode with the insulating layer interposed therebetween.

According to a fifth embodiment of the present technology, there isprovided an electronic apparatus including a semiconductor deviceincluding a semiconductor substrate, an insulating layer formed on thesemiconductor substrate, a joining electrode formed on a surface of theinsulating layer, and a protective layer formed on a surface of theinsulating layer and surrounding the joining electrode with theinsulating layer interposed therebetween, and a signal processingcircuit for processing an output signal of the semiconductor device.

The above and other features and advantages of the present technologywill become apparent from the following description and the appendedclaims, taken in conjunction with the accompanying drawings in whichlike parts or elements denoted by like reference characters.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing an example of a semiconductor deviceto which an embodiment of the present technology is applied;

FIG. 2 is a partial sectional view showing a configuration of asemiconductor device according to a first embodiment of the presenttechnology;

FIGS. 3A to 3F are schematic sectional views illustrating differentsteps of a production process of a sensor substrate in fabrication ofthe semiconductor device of FIG. 2;

FIGS. 4A to 4E are schematic sectional views illustrating differentsteps of a production process of a circuit board in fabrication of thesemiconductor device of FIG. 2;

FIGS. 5A and 5B are schematic sectional views illustrating differentsteps of bonding in fabrication of the semiconductor device of FIG. 2;

FIGS. 6A to 6C, 6A′ to 6C′ and 6D are schematic sectional viewsillustrating an example of a fabrication method of a semiconductordevice as a comparative example to the semiconductor device of FIG. 2;

FIG. 7 is a partial schematic sectional view showing a configuration ofa semiconductor device which is a modification to the semiconductordevice of FIG. 2;

FIG. 8 is a partial sectional view showing a configuration of asemiconductor device according to a second embodiment of the presenttechnology;

FIGS. 9A to 9E are schematic sectional views illustrating a productionprocedure of a first substrate or sensor substrate in fabrication of asemiconductor device according to the second embodiment of the presenttechnology;

FIGS. 10A and 10B are schematic sectional views illustrating aproduction procedure of a second substrate or circuit substrate infabrication of the semiconductor device according to the secondembodiment;

FIGS. 11A and 11B are schematic sectional views illustrating differentsteps of bonding in fabrication of the semiconductor device according tothe second embodiment;

FIGS. 12A and 12B are schematic sectional views illustrating a problemwhich occurs upon Cu—Cu joining;

FIG. 13 is a schematic sectional view illustrating another problem whichoccurs upon Cu—Cu joining;

FIG. 14 is a schematic sectional view in the proximity of a joininginterface of a semiconductor device according to a first working exampleof a third embodiment of the disclosed technology;

FIG. 15 is a schematic top plan view in the proximity of a joininginterface of the semiconductor device of FIG. 14;

FIGS. 16A to 16M are schematic sectional views illustrating differentsteps of a production procedure of the semiconductor device of FIG. 15;

FIG. 17 is a schematic sectional view in the proximity of a joininginterface of a semiconductor device according to a second workingexample of the third embodiment of the disclosed technology;

FIG. 18 is a schematic top plan view in the proximity of a joininginterface of the semiconductor device of FIG. 17;

FIGS. 19A to 19E are schematic sectional views illustrating differentsteps of a production procedure of the semiconductor device of FIG. 17;

FIG. 20 is a schematic sectional view in the proximity of a joininginterface of a semiconductor device according to a third working exampleof the third embodiment of the disclosed technology;

FIG. 21 is a schematic top plan view in the proximity of a joininginterface of the semiconductor device of FIG. 20;

FIGS. 22A to 22H are schematic sectional views illustrating differentsteps of a production procedure of the semiconductor device of FIG. 20;

FIG. 23 is a schematic sectional view in the proximity of a joininginterface of a semiconductor device according to a modification 1;

FIG. 24 is a schematic sectional view illustrating a productionprocedure of the semiconductor device of FIG. 23;

FIGS. 25 and 26 are schematic sectional views in the proximity of ajoining interface of semiconductor devices according to modifications 3and 4;

FIGS. 27 and 28 are schematic sectional views in the proximity of ajoining interface of semiconductor devices according to referenceexamples 1 and 2;

FIGS. 29 and 30 are schematic views illustrating problems which mayoccur in an existing Cu—Cu joining technique;

FIG. 31 is a schematic sectional view in the proximity of a joininginterface of a semiconductor device according to a fourth workingexample of the third embodiment of the disclosed technology;

FIG. 32 is a schematic top plan view in the proximity of a joininginterface of the semiconductor device of FIG. 31;

FIGS. 33A to 33D are schematic sectional views illustrating differentsteps of a production procedure of the semiconductor device of FIG. 31;

FIG. 34 is a schematic sectional view in the proximity of a joininginterface of a semiconductor device according to a fifth working exampleof the third embodiment of the disclosed technology;

FIG. 35 is a schematic top plan view in the proximity of a joininginterface of the semiconductor device of FIG. 34;

FIGS. 36A to 36D are schematic sectional views illustrating differentsteps of a production procedure of the semiconductor device of FIG. 34;

FIG. 37 is a schematic sectional view showing an example of aconfiguration of a semiconductor device of an application example 1 towhich the Cu—Cu joining technique of the disclosed technology can beapplied;

FIG. 38 is a schematic sectional view showing an example of aconfiguration of a semiconductor device of an application example 2 towhich the Cu—Cu joining technique of the disclosed technology can beapplied;

FIG. 39 is a schematic sectional view showing a general configuration ofa joining electrode of a semiconductor device according to a fourthembodiment of the disclosed technology;

FIG. 40A is a schematic sectional view showing a general configurationof the semiconductor device including the joining electrode of FIG. 39and FIG. 40B is a plan view of a joining face of a first joining portionshown in FIG. 40A;

FIGS. 41A to 41K are schematic views illustrating different steps offabrication of the semiconductor device of FIG. 40A;

FIG. 42A is a schematic sectional view showing a general configurationof a semiconductor device including a joining electrode of amodification 1 to that of FIG. 39 and FIG. 42B is a plan view of ajoining face of a first joining portion shown in FIG. 42A;

FIGS. 43A to 43G are schematic sectional views illustrating differentsteps of fabrication of the semiconductor device of FIG. 42A;

FIG. 44 is a schematic sectional view showing a general configuration ofa semiconductor device including a joining electrode of a modification 2to that of FIG. 39; and

FIG. 45 is a block diagram showing an electronic apparatus whichincludes a semiconductor device obtained by applying the presenttechnology.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS First Embodiment 1.Example of the General Configuration of the Semiconductor Device of theFirst Embodiment

FIG. 1 shows a general configuration of a solid-state image pickupdevice as an example of a semiconductor device of a three-dimensionalstructure to which the present technology is applied. Referring to FIG.1, the semiconductor device 1 shown is a semiconductor device of athree-dimensional structure, that is, a solid-state image pickupapparatus, which includes a sensor substrate 2 as a first substrate, anda circuit substrate 7 as a second substrate bonded in a laminated stateto the sensor substrate 2. In the following description, the sensorsubstrate 2 as a first substrate is referred to merely as sensorsubstrate 2, and the circuit substrate 7 as a second substrate isreferred to merely as circuit substrate 7.

A pixel region 4 in which a plurality of pixels 3 each including aphotoelectric conversion element are arrayed regularly two-dimensionallyis provided on one face side of the sensor substrate 2. The pixel region4 has a plurality of pixel driving lines 5 laid therein in a rowdirection and has a plurality of vertical signal lines 6 laid therein ina column direction. The pixels 3 are disposed such that each thereof isconnected to one of the pixel driving lines 5 and one of the verticalsignal lines 6. Each of the pixels 3 includes a pixel circuit configuredfrom a photoelectric conversion element, a charge accumulation portion,a plurality of transistors each in the form of a MOS (metal oxidesemiconductor) transistor, a capacitive element and so forth. It is tobe noted that a plurality of pixels may commonly use some pixel circuit.

Further, on one face side of the circuit substrate 7, peripheralcircuits such as a vertical driving circuit 8, a column signalprocessing circuit 9, a horizontal driving circuit 10 and a systemcontrolling circuit 11 for controlling the pixels 3 provided on thesensor substrate 2 are provided.

2. Configuration of the Semiconductor Device of the First Embodiment

FIG. 2 shows a cross sectional configuration of the semiconductor deviceof the first embodiment and shows a cross section of three pixels shownin FIG. 1. In the following, a detailed configuration of thesemiconductor device of the first embodiment is described with referenceto the cross section of FIG. 2.

The semiconductor device 1 shown is a solid-state image pickup device ofa three-dimensional structure wherein the sensor substrate 2 and thecircuit substrate 7 are bonded in a laminated relationship to each otheras described above. The sensor substrate 2 is configured from asemiconductor layer 2 a, and a wiring line layer 2 b and an electrodelayer 2 c disposed on a face of the semiconductor layer 2 a on thecircuit substrate 7 side. The circuit substrate 7 is configured from asemiconductor layer 7 a, and a first wiring line layer 7 b, a secondwiring line layer 7 c and an electrode layer 7 d disposed on a face ofthe semiconductor layer 7 a on the sensor substrate 2 side.

The sensor substrate 2 and the circuit substrate 7 configured in such amanner as described above are bonded to each other at the surface of theelectrode layer 2 c and the surface of the electrode layer 7 d asbonding faces. The semiconductor device 1 of the present embodiment ischaracterized in the configuration of the electrode layer 2 c and theelectrode layer 7 d as hereinafter described in detail.

Further, on the face of the sensor substrate 2 on the opposite side tothe circuit substrate 7, a protective film 15, a color filter layer 17and on-chip lenses 19 are laminated in order.

Now, a detailed confirmation of the layers configuring the sensorsubstrate 2 and the circuit substrate 7 is described successively, and aconfiguration of the protective film 15, color filter layer 17 andon-chip lenses 19 is described successively.

[Semiconductor Layer 2 a (Sensor Substrate 2 Side)]

The semiconductor layer 2 a of the sensor substrate 2 side is formed bya semiconductor substrate made of, for example, single crystal siliconin the form of a thin film. In the semiconductor layer 2 a, aphotoelectric conversion portion 21 formed, for example, from an n-typeimpurity layer or a p-type impurity layer is provided for each pixel ona first face side on which the color filter layer 17, on-chip lenses 19and so forth are disposed. Meanwhile, on a second face side of thesemiconductor layer 2 a, a floating diffusion FD and a source/drain 23of a transistor Tr made of, for example, an n+ type impurity layer, adifferent impurity layer not shown and so forth are provided.

[Wiring Line Layer 2 b (Sensor Substrate 2 Side)]

The wiring line layer 2 b provided on the semiconductor layer 2 a of thesensor substrate 2 has, on the interface side thereof with thesemiconductor layer 2 a, for each pixel, a transfer gate TG and a gateelectrode 27 of a transistor Tr provided thereon with a gate insulatingfilm 25 interposed therebetween, and other electrodes not shown. Thetransfer gate TG and the gate electrode 27 are covered with aninterlayer insulating film 29, and an embedded wiring line 31 of, forexample, Cu is provided in a groove pattern provided in the interlayerinsulating film 29.

In this instance, the interlayer insulating film 29 is configured using,for example, silicon oxide. On the other hand, where the embedded wiringlines 31 are laid out densely, the interlayer insulating film 29 may beconfigured using a material having a dielectric constant lower than thatof silicon oxide in order to reduce the capacitance between the embeddedwiring lines 31. In such an interlayer insulating film 29 as justdescribed, groove patterns open to the circuit substrate 7 side areformed such that they partly extend to the transfer gates TG or the gateelectrodes 27.

In each of such groove patterns as described above, a wiring line layer31 b made of copper (Cu) is provided with a barrier metal layer 31 ainterposed therebetween, and the embedded wiring lines 31 are configuredfrom the two layers. The barrier metal layer 31 a is a layer forpreventing diffusion of copper (Cu) into the interlayer insulating film29 made of silicon oxide or a material having a dielectric constantlower than that of silicon oxide and is configured using, for example,tantalum (Ta) or tantalum nitride (TaN).

It is to be noted that such a wiring line layer 2 b as described abovemay be configured as a laminated multilayer wiring line layer.

[Electrode Layer 2 c (Sensor Substrate 2 Side)]

The electrode layer 2 c on the sensor substrate 2 side provided on thewiring line layer 2 b includes, for each pixel, a first electrode 33 ledout to the surface of the sensor substrate 2 on the circuit substrate 7side, and a first insulating film 35 for covering the periphery of thefirst electrode 33. The first electrode 33 and the first insulating film35 configure a bonding face 41 of the sensor substrate 2 to the circuitsubstrate 7.

The first electrode 33 is configured from a single material layer using,for example, copper (Cu). Such a first electrode 33 as just described isconfigured as an embedded wiring line embedded in the first insulatingfilm 35.

The first insulating film 35 is provided in such a manner as to coverthe wiring line layer 2 b and includes a groove pattern 35 a open to thecircuit substrate 7 side and a first electrode 33 embedded in the groovepattern 35 a. In other words, the first insulating film 35 is providedin contact with the periphery of the first electrode 33. It is to benoted that, though not shown, the groove pattern 35 a provided in thefirst insulating film 35 partly extends to the embedded wiring line 31embedded in the wiring line layer 2 b and the first electrode 33embedded in this manner is connected to the embedded wiring line 31 asoccasion demands.

Such a first insulating film 35 as described above is configured from adiffusion preventing material with respect to a material from which thefirst electrode 33 is configured. As such a diffusion preventingmaterial as just described, a material having a low diffusioncoefficient with respect to a material which configures the firstelectrode 33 is used. Particularly in the present embodiment, the firstinsulating film 35 is configured as a single material layer for which adiffusion preventing material is used is configured. Further, in thepresent embodiment, the first insulating film 35 is configured from adiffusion preventing material not only with respect to the firstelectrode 33 but also with respect to a material which configures asecond electrode 67 led out to the surface of the circuit substrate 7 onthe sensor substrate 2 side.

For example, if the first electrode 33 and the second electrode 67 areconfigured using copper (Cu), then as the diffusion preventing materialwhich configures the first insulating film 35, an inorganic insulatingmaterial or an organic insulating material having a molecular structuredenser than that of silicon oxide is used. As such an inorganicinsulation material, silicon nitride (SiN), silicon carbonitride (SiCN),silicon oxynitride (SiON) and silicon carbide (SiC) are applicable.Meanwhile, as the organic insulating material, benzocyclobutene (BCB),polybenzoxazole (PBO), polyimide and polyallyl ether (PAE) areapplicable. It is to be noted that, since the electrode layer 2 c is theuppermost layer on the sensor substrate 2 side, also the layout of thefirst electrodes 33 is rough. Therefore, the capacitance is less likelyto be formed between the first electrodes 33, and a low dielectricconstant is not demanded for the first insulating film 35.

As described above, the surface of the sensor substrate 2 on the circuitsubstrate 7 is configured as the bonding face 41 to the circuitsubstrate 7 and is in a state in which it is configured only from thefirst electrode 33 and the first insulating film 35. This bonding face41 is configured as a flattened face.

[Semiconductor Layer 7 a (Circuit Substrate 7 Side)]

The semiconductor layer 7 a on the circuit substrate 7 side is formed byforming a semiconductor substrate made of, for example, single crystalsilicon as a thin film. On the surface layer of the semiconductor layer7 a on the sensor substrate 2 side, a source/drain 51 of a transistor Trand an impurity layer and so forth which are not shown in FIG. 2 areprovided for each pixel.

[First Wiring Line Layer 7 b (Circuit Substrate 7 Side)]

The first wiring line layer 7 b on the circuit substrate 7 side has, onan interface side thereof with the semiconductor layer 7 a, for eachpixel, a gate electrode 55 provided thereon with a gate insulating film53 interposed therebetween and other electrodes not shown in FIG. 2. Thegate electrode 55 and other electrodes are covered with an interlayerinsulating film 57, and embedded wiring lines 59 formed using, forexample, copper (Cu) are provided in groove patterns provided in theinterlayer insulating film 57.

The interlayer insulating film 57 and the embedded wiring lines 59 havea configuration similar to that of the wiring line layer 2 b of thesensor substrate 2 side.

In particular, on the interlayer insulating film 57, groove patternsopen to the sensor substrate 2 side are formed such that they partlyextend to the gate electrode 55 or the source/drain 51. Further, awiring line layer 59 b made of copper (Cu) is provided in such groovepatterns with a barrier metal layer 59 a interposed between, and theembedded wiring lines 59 are configured from the two layers.

[Second Wiring Line Layer 7 c (Circuit Substrate 7 Side)]

The second wiring line layer 7 c on the circuit substrate 7 sideincludes, on an inter face side thereof with the first wiring line layer7 b, an interlayer insulating film 63 laminated with a diffusionpreventing insulating layer 61 interposed therebetween. An embeddedwiring line 65 formed using, for example, copper (Cu) is provided ineach of groove patterns provided in the diffusion preventing insulatinglayer 61 and the interlayer insulating film 63.

The diffusion preventing insulating layer 61 is configured from adiffusion preventing material with respect to the material whichconfigures the embedded wiring lines 59 provided in the first wiringline layer 7 b. Such a diffusion preventing insulating layer 61 as justdescribed is formed, for example, from silicon nitride (SiN), siliconcarbonitride (SiCN), silicon oxynitride (SiON) or silicon carbide (SiC).

The interlayer insulating film 63 and the embedded wiring lines 65 havea configuration similar to that of the wiring line layer 2 b on thesensor substrate 2 side. In particular, the interlayer insulating film63 has groove patterns formed thereon so as to open to the sensorsubstrate 2 side and partly extend to the embedded wiring lines 59 ofthe first wiring line layer 7 b. Further, a wiring line layer 65 b madeof copper (Cu) is provided in such groove patterns as just describedwith a barrier metal layer 65 a interposed therebetween, and theembedded wiring lines 65 are configured from the two layers.

It is to be noted that such a first wiring line layer 7 b and a secondwiring line layer 7 c as described above may be configured as alaminated multiplayer wiring line layer.

[Electrode Layer 7 d (Circuit Substrate 7 Side)]

The electrode layer 7 d of the circuit substrate 7 side which is asecond substrate includes, for each pixel, a second electrode 67 led outto the surface of the circuit substrate 7 on the sensor substrate 2 sideand bonded to the first electrode 33, and a second insulating film 69which covers the periphery of the second electrode 67. The secondelectrode 67 and the second insulating film 69 configure a bonding face71 of the circuit substrate 7 to the sensor substrate 2 and areconfigured similarly to the electrode layer 2 c of the sensor substrate2 side as described below.

In particular, the second electrode 67 is formed from a single materiallayer and is configured from a material which can keep good bondabilityto the first electrode 33 provided on the sensor substrate 2 side.Therefore, the second electrode 67 may be configured from the samematerial as that of the first electrode 33 and configured, for example,using copper (Cu). Such a second electrode 67 as just described isconfigured as an embedded wiring line embedded in the second insulatingfilm 69.

Further, the second insulating film 69 is configured in such a manner asto cover the second wiring line layer 7 c, and has, for each pixel, agroove pattern 69 a open to the sensor substrate 2 side and having asecond electrode 67 embedded therein. In other words, the secondinsulating film 69 is provided in contact with the periphery of thesecond electrode 67. It is to be noted that the groove pattern 69 aprovided in the second insulating film 69 partly extends to the embeddedwiring line 65 which is an underlying layer, and the second electrode 67embedded in the groove pattern 69 a is connected to the embedded wiringline 65 as occasion demands.

Such a second insulating film 69 as described above is configured from adiffusion preventing material with respect to the material whichconfigures the second electrode 67. Particularly in the presentembodiment, the second insulating film 69 is configured as a singlematerial layer for which a diffusion preventing material is used isconfigured. Further, in the present embodiment, the second insulatingfilm 69 is configured from a diffusion preventing material not only withrespect to the second electrode 67 but also with respect to the materialwhich configures the first electrode 33 led out to the bonding face ofthe sensor substrate 2 to the circuit substrate 7.

Such a second insulating film 69 as just described can be formed using amaterial selected from the materials listed with regard to the firstinsulating film 35 provided on the sensor substrate 2 side. It is to benoted that the second insulating film 69 is configured from a materialwith which good bondability can be kept to the first insulating film 35on the sensor substrate 2 side. Therefore, the second insulating film 69may be configured from the same material as that of the first insulatingfilm 35. Further, since the electrode layer 7 d is the uppermost layeron the circuit substrate 7 side. Also the second electrodes 67 may belaid out roughly. Therefore, the second electrodes 67 are less likely tohave capacitance therebetween, and a low dielectric constant is notdemanded for the second insulating film 69.

As described above, the surface of the circuit substrate 7 on the sensorsubstrate 2 side is configured as the bonding face 71 to the sensorsubstrate 2 and is configured only from the second electrode 67 and thesecond insulating film 69. This bonding face 71 is configured as aflattened face.

[Protective Film 15]

The protective film 15 which covers the photoelectric conversionportions 21 of the sensor substrate 2 is configured from a material filmhaving a passivation property and configured using, for example, asilicon oxide film, a silicon nitride film or a silicon oxynitride film.

[Color Filter Layer 17]

The color filter layer 17 is configured from color filters provided in a1:1 corresponding relationship to the photoelectric conversion portions21. The array of the color filters of the colors is not restricted.

[On-Chip Lens 19]

The on-chip lenses 19 are provided in a 1:1 corresponding relationshipto each of the color filters of the colors which configure thephotoelectric conversion portions 21 and the color filter layers 17 andare configured so as to condense incident light upon the photoelectricconversion portions 21.

[Working Effect of the Semiconductor Device of the First Embodiment]

With the semiconductor device 1 configured in such a manner as describedabove, since it is structured such that the periphery of the firstelectrode 33 is covered with the first insulating film 35 configuredfrom a diffusion preventing material with respect to the first electrode33, there is no necessity to provide a barrier metal layer between thefirst electrode 33 and the first insulating film 35. Similarly, sincethe semiconductor device 1 is structured such that the periphery of thesecond electrode 67 is covered with the second insulating film 69configured from a diffusion preventing material with respect to thesecond electrode 67, there is no necessity to provide a barrier metallayer between the second electrode 67 and the second insulating film 69.

Therefore, while the bonding face 41 of the sensor substrate 2 and thebonding face 71 of the circuit substrate 7 are configured only from theinsulating films 35 and 69 and the electrodes 33 and 67, respectively,to assure bonding strength, diffusion of the materials configuring theelectrodes 33 and 67 into the insulating films 35 and 69 can beprevented.

As a result, in the semiconductor device 1 of a three-dimensionalstructure in which bonding between the electrodes 33 and 67 isestablished by bonding between the sensor substrate 2 and the circuitsubstrate 7, while diffusion of the electrode materials into theinsulating films 35 and 69 is prevented, bonding strength is assured,and enhancement of the reliability can be anticipated.

3. Production Procedure of the Sensor Substrate in the Structure of theSemiconductor Device of the First Embodiment

FIGS. 3A to 3F illustrate different steps of a production procedure ofthe sensor substrate used in fabrication of the semiconductor device ofthe configuration described hereinabove in connection with the firstembodiment. In the following, a production procedure of the sensorsubstrate used in the present embodiment is described.

[FIG. 3A]

First, a semiconductor substrate 20 made of, for example, single crystalsilicon is prepared as shown in FIG. 3A. A photoelectric conversionportion 21 made of an n-type impurity is formed, for each pixel, at apredetermined depth of the semiconductor substrate 20, and then a chargetransfer portion formed from an n+ type impurity layer and a chargeaccumulation portion for holes formed from a p+ type impurity layer areformed on a surface layer of the photoelectric conversion portion 21. Afloating diffusion FD, a source/drain 23 and a further impurity layernot shown formed from an n+ type impurity layer are formed on thesurface layer of the semiconductor substrate 20.

Further, a gate insulating film 25 is formed on the surface of thesemiconductor substrate 20, and a transfer gate TG and a gate electrode27 are formed on the gate insulating film 25. The transfer gate TG isformed between the floating diffusion FD and the photoelectricconversion portion 21, and the gate electrode 27 is formed between thesource/drain 23. Further, at the same step, also other electrodes notshown are formed.

Thereafter, an interlayer insulating film 29 made of, for example,silicon oxide is formed on the semiconductor substrate 20 in such astate in which it covers the transfer gates TG and the gate electrodes27.

[FIG. 3B]

Then, groove patterns 29 a are formed on the interlayer insulating film29 as shown in FIG. 3B. The groove patterns 29 a are formed in a shapein which they extend at necessary places to the transfer gates TG.Further, though not shown in FIG. 3B, groove patterns extending to thesources/drains 23 are formed in the interlayer insulating film 29 andthe gate insulating film 25 as occasion demands.

Then, a barrier metal layer 31 a is formed in such a state that itcovers the inner wall of the groove patterns 29 a, and a wiring linelayer 31 b made of copper (Cu) is formed in a state in which it isembedded in the groove patterns 29 a.

[FIG. 3C]

Thereafter, as shown in FIG. 3C, the wiring line layer 31 b is removedand flattened by a chemical mechanical polishing (hereinafter CMP)method until the barrier metal layer 31 a is exposed, and then thebarrier metal layer 31 a is removed and flattened until the interlayerinsulating film 29 is exposed. Consequently, embedded wiring lines 31 inwhich the wiring line layer 31 b is embedded with the barrier metallayer 31 a interposed therebetween are formed in the groove patterns 29a thereby to obtain a wiring line layer 2 b which includes the embeddedwiring lines 31.

The steps described above are not particularly restricted in the stepprocedure and may be carried out in a suitably selected ordinary stepprocedure. In the present technology, the following steps arecharacteristic steps.

[FIG. 3D]

In particular, a first insulating film 35 is formed on the wiring linelayer 2 b as shown in FIG. 3D. The first insulating film 35 is formedusing a diffusion preventing material with respect to a material whichconfigures a first electrode film to be formed next. For example, wherethe first electrode film is made of copper (Cu), the first insulatingfilm 35 is formed using an inorganic insulating material or an organicinsulating material having a molecular structure denser than siliconoxide. As such an inorganic insulating material as just described,silicon nitride (SiN), silicon carbonitride (SiCN), silicon oxynitride(SiON) and silicon carbide (SiC) are applicable. Meanwhile, as theorganic insulating material, benzocyclobutene (BCB), polybenzoxazole(PBO), polyimide and polyallyl ether (PAE) are applicable.

The first insulating film 35 made of any of such materials as describedabove is formed by a formation method suitable for the material. Forexample, if an inorganic insulating material is used, then a chemicalvapor deposition method (CVD) is applied, but if an organic insulatingmaterial is used, then a CVD method or an application method is applied.

Then, groove patterns 35 a are formed in the first insulating film 35.The groove patterns 35 a have a shape in which electrode pads areembedded and extend at necessary places not shown to the embedded wiringlines 31 of the lower layer.

Such groove patterns 35 a are formed in the following manner. Forexample, if the first insulating film 35 is made of an inorganicinsulating material, then a resist pattern is formed on the firstinsulating film 35 by a photolithography method first, and then thefirst insulating film 35 is etched using the resist pattern as a mask.On the other hand, if the first insulating film 35 is made of an organicinsulating material, then an inorganic material layer is formed on thefirst insulating film 35 first, and then a resist pattern is formed onthe inorganic material layer. Then, the inorganic material layer isetched using the resist pattern as a mask to form an inorganic mask, andthe first insulating film 35 is etched from above the inorganic mask.Groove patterns 35 a are formed by the etching, and thereafter, theinorganic mask is removed from the first insulating film 35.

[FIG. 3E]

Thereafter, a first electrode film 33 a is formed directly on the firstinsulating film 35 in a state in which it embeds the groove patterns 35a as seen in FIG. 3E. The first electrode film 33 a is made of amaterial whose diffusion into the first insulating film 35 is preventedand is configured, for example, using copper (Cu). Formation of such afirst electrode film 33 a as just described is carried out by forming athin seed layer, for example, by a sputtering method and then using aplating method wherein the seed layer is used as an electrode.

[FIG. 3F]

Then, the first electrode film 33 a formed directly on the firstinsulating film 35 is removed and flattened by a CMP method until thefirst insulating film 35 is exposed as seen in FIG. 3F. Thereupon, usingthe first insulating film 35 as a polishing stopper, such CMP that thepolishing stops automatically is carried out in order from the firstelectrode film 33 a portion around which the first insulating film 35 isexposed in the polishing face. It is only necessary that the firstelectrode film 33 a be made from a material which chemically active astypified by copper (Cu) to carry out such CMP. Various methods are usedas follows.

For example, in a region around which the first insulating film 35 isexposed by advancement of the polishing by the CMP of the firstelectrode film 33 a, a local temperature variation of polishing slurryor a local variation of the population of the first electrode film 33 aon the polishing face occurs. Therefore, a method is recommendablewherein a chemical action which utilizes such local variations isutilized to locally and automatically stop the advancement of thepolishing by the CMP in a region of the first electrode film 33 a aroundwhich the first insulating film 35 is exposed.

Another method may be used wherein only the surface of the firstelectrode film 33 a is degenerated and polishing is advanced only at aposition at which a polishing pad contacts without using a chemicaletching action. In this instance, in the region of the first electrodefilm 33 a around which the first insulating film 35 is exposed by theadvancement of the polishing by the CMP of the first electrode film 33a, the surface of the first insulating film 35 is used as a referenceplane and the polishing does not advance any more. Therefore, thepolishing stops automatically in order beginning with the region of thefirst electrode 33 around which the first insulating film 35 is exposed.In particular, such CMP is carried out by using abrasive grain-lesspolishing slurry for Cu “HS-C430” (product name by Hitachi Chemical Co.,Ltd.) as the polishing slurry.

From the foregoing, the first electrodes 33 in which the first electrodefilm 33 a is embedded are formed as embedded electrodes in the groovepatterns 35 a to obtain the electrode layer 2 c which includes the firstelectrodes 33. By this, the sensor substrate 2 which has the flattenedbonding face 41 configured from the first electrodes 33 and the firstinsulating film 35 is produced as a first substrate.

4. Production Procedure of the Circuit Substrate in Fabrication of theSemiconductor Device of the First Embodiment

FIGS. 4A to 4E illustrate a production procedure of a circuit substratefor use with fabrication of the semiconductor device of theconfiguration described hereinabove in connection with the firstembodiment. In the following, the production procedure of the circuitsubstrate used in the embodiment is described with reference to FIGS. 4Ato 4E.

[FIG. 4A]

First, a semiconductor substrate 50 made of, for example, single crystalsilicon is prepared as shown in FIG. 4A. Sources/drains 51 of individualconductive types and other impurity layers not shown in FIG. 4A areformed on a surface layer of the semiconductor substrate 50. Further, agate insulating film 53 is formed on the surface of the semiconductorsubstrate 50, and gate electrodes 55 are formed on the gate insulatingfilm 53. The gate electrodes 55 are formed between the sources/drains61. Further, at the same step, the other electrodes not shown areformed.

Thereafter, an interlayer insulating film 57 made of, for example,silicon oxide is formed on the semiconductor substrate 50 in such astate that it covers the gate electrodes 55.

Thereafter, groove patterns 57 a are formed in the interlayer insulatingfilm 57. The groove patterns 57 a are formed in a shape in which theextend to the gate electrodes 55 at necessary places. Further, thoughnot shown in FIG. 4A, groove patterns extending to the sources/drains 51are formed at necessary places in the interlayer insulating film 57 andthe gate insulating film 53. Then, a barrier metal layer 59 a is formedin a state in which it covers the inner wall of the groove patterns 57a, and a wiring line layer 59 b made of copper (Cu) is formed on thebarrier metal layer 59 a in such a state that it embeds the groovepatterns 57 a. Thereafter, the wiring line layer 59 b and the barriermetal layer 59 a are successively flattened and removed by CMP. By this,embedded wiring lines 59 in which wiring line layer 59 b is embeddedwith the barrier metal layer 59 a interposed therebetween are formed inthe groove patterns 57 a to obtain a first wiring line layer 7 b whichincludes the embedded wiring lines 59.

[FIG. 4B]

As shown in FIG. 4B, an interlayer insulating film 63 is laminated toform a film on the first wiring line layer 7 b with the diffusionpreventing insulating layer 61 interposed therebetween to form groovepatterns 63 a in the interlayer insulating film 63 and the diffusionpreventing insulating layer 61. The groove patterns 63 a are formed soas to extend to the embedded wiring lines 59 of the lower layer atnecessary places. Thereafter, a wiring line layer 65 b is embedded intothe groove patterns 63 a with a barrier metal layer 65 a interposedtherebetween to form embedded wiring lines 65 thereby to obtain a secondwiring line layer 7 c.

The steps described above may be carried out in an ordinary stepprocedure, and are not limited to a specific step procedure but can becarried out by a suitable procedure. In the present technology, stepsdescribed below are characteristic steps.

[FIG. 4C]

First, a second insulating film 69 is formed on the second wiring linelayer 7 c as shown in FIG. 4C. The second insulating film 69 is formedusing a diffusion preventing material with respect to the material whichconfigures a second conductive film to be formed next. For example, ifthe second electrode layer is made of copper (Cu), then the secondinsulating film 69 is configured using a material similar to that thatof the first insulating film 35 on the sensor substrate 2 side describedhereinabove and is formed as a film.

Then, groove patterns 69 a are formed in the second insulating film 69.The groove patterns 69 a have a shape in which electrode pads areembedded, and extend at necessary places to the embedded wiring lines 65formed in the second wiring line layer 7 c. Formation of such groovepatterns 69 a is carried out similarly to that of the groove patterns 35a formed in the first insulating film 35 on the sensor substrate 2 sidedescribed hereinabove.

[FIG. 4D]

Then as shown in FIG. 4D, a second electrode film 67 a is directlyformed on the second insulating film 69 in a state in which it embedsthe groove patterns 69 a therein. The second electrode film 67 a is madeof a material whose diffusion into the second insulating film 69 isprevented, and is configured, for example, using copper (Cu). Formationof such the second electrode film 67 a as just described is carried out,for example, by forming a thin seed film by a sputtering method and thencarrying out a plating method using the seed layer as an electrode.

[FIG. 4E]

Then, as shown in FIG. 4E, the second electrode film 67 a is flattenedand removed by a CMP method until the second insulating film 69 isexposed. The flattening of the second electrode film 67 a is carried outby CMP wherein polishing stops automatically in order beginning with aportion of the second electrode film 67 a around which the secondinsulating film 69 is exposed in the polishing face using the secondinsulating film 69 as a polishing stopper similarly as in the flatteningof the first electrode film 33 a described hereinabove with reference toFIG. 3F.

By the procedure described above, the second electrodes 67 in which thesecond electrode film 67 a is embedded are formed in the groove patterns69 a to obtain an electrode layer 7 d which includes the secondelectrodes 67 as embedded electrodes. Further, a circuit substrate 7having a bonding face 71 configured from the second electrode 67 and thesecond insulating film 69 is produced as a second substrate.

5. Bonding of the Substrates in Fabrication of the Semiconductor Deviceof the First Embodiment

Now, a bonding procedure of the sensor substrate 2 on which the flatbonding face 41 is formed and the circuit substrate 7 on which the flatbonding face 71 is formed to each other is described with reference toFIGS. 5A and 5B.

[FIG. 5A]

First, as seen in FIG. 5A, the sensor substrate 2 and the circuitsubstrate 7 configured by the procedures described above are disposed inan opposing relationship to each other with the flat bonding face 41 andthe flat bonding face 71 opposed to each other. Further, the sensorsubstrate 2 and the circuit substrate 7 are positioned such that thefirst electrodes 33 of the sensor substrate 2 side and the secondelectrodes 67 of the circuit substrate 7 side correspond to each other.In the example illustrated, while the first electrodes 33 and the secondelectrodes 67 are in a state in which they correspond in a 1:1corresponding relationship to each other, the corresponding relationshipof the sensor substrate 2 and the circuit substrate 7 is not limited tothis.

It is to be noted that, for the bonding face 41 of the sensor substrate2 and the bonding face 71 of the circuit substrate 7, pre-processing forbonding by a wet process or a plasma process is carried out as occasiondemands.

[FIG. 5B]

Then, as shown in FIG. 5B, the sensor substrate 2 and the circuitsubstrate 7 are laminated such that the bonding face 41 and the bondingface 71 contact with each other. Then, heat treatment is carried out inthis state to bond the first electrodes 33 of the bonding face 41 andthe second electrodes 67 of the bonding face 71 to each other. Further,the first insulating film 35 of the bonding face 41 and the secondinsulating film 69 of the bonding face 71 are bonded to each other. Suchheat treatment is carried out at a temperature and for time sufficientto allow the electrodes 33 and 67 to be bonded to each other within arange within which the heat treatment does not have an influence on theelements and wiring lines formed on the sensor substrate 2 and thecircuit substrate 7 based on the materials which configure the firstelectrodes 33 and the second electrodes 67.

For example, in the case where the first electrodes 33 and the secondelectrodes 67 are configured from materials containing copper (Cu) as aprincipal component, heat treatment is carried out at 200 to 600° C. forapproximately one to five hours. Such heat treatment may be carried outunder a pressurized atmosphere or may be carried out in a state in whichthe sensor substrate 2 and the circuit substrate 7 are pressed to eachother from the opposite face sides. As an example, heat treatment at400° C. for four hours is carried out to carry out Cu—Cu joining.

After the sensor substrate 2 and the circuit substrate 7 are laminatedand bonded at the joining faces 41 and 71 to each other in such a manneras described above, the semiconductor substrate 20 of the sensorsubstrate 2 side is thinned into a semiconductor layer 2 a to expose thephotoelectric conversion portion 21. Further, as occasion demands, thesemiconductor substrate 50 of the circuit substrate 7 is thinned to forma semiconductor layer 7 a.

[FIG. 2]

Thereafter, a protective film 15 is formed on the exposed face of thephotoelectric conversion portions 21 of the sensor substrate 2 as shownin FIG. 2, and then a color filter layer 17 and on-chip lenses 19 areformed on the protective film 15 thereby to complete a semiconductordevice 1 which is a solid-state image pickup device.

[Working Effects of the Fabrication Method of the Semiconductor Deviceof the First Embodiment]

With the fabrication method according to the first embodiment describedabove, as described hereinabove with reference to FIG. 3F, in formationof the sensor substrate 2, the first electrode films 33 a formeddirectly on the first insulating film 35 are flattened and removed byCMP in which the first insulating film 35 is used as a polishingstopper. Thereupon, since the CMP in which polishing is stoppedautomatically is carried out in order beginning with the portion of thefirst electrode film 33 a around which the first insulating film 35 isexposed, occurrence of dishing or erosion can be prevented over theoverall area of the polishing face, and a flat polished face can beobtained as the bonding face 41.

Further, also at the step described hereinabove with reference to FIG.4E, a flat polished face can be obtained as the bonding face 71similarly as in the foregoing description.

Accordingly, at the bonding step described hereinabove with reference toFIGS. 5A and 5B, the sensor substrate 2 and the circuit substrate 7 arebonded to each other between the flat bonding face 41 and the flatbonding face 71 thereof. Consequently, bonding by which good joiningbetween the electrodes 33 and 67 is established is carried out over theoverall area of the bonding face 41 and the bonding face 71, and highbonding strength between the sensor substrate 2 and the circuitsubstrate 7 can be maintained.

Further, the first insulating film 35 which configures the bonding face41 of the sensor substrate 2 side is configured from a diffusionpreventing material with respect to the first electrode 33. Therefore,diffusion of the first electrodes 33 into the first insulating film 35can be prevented. Similarly, the second insulating film 69 whichconfigures the bonding face 71 of the circuit substrate 7 side isconfigured from a diffusion preventing material with respect to thesecond electrode 67. Therefore, diffusion of the second electrodes 67into the second insulating film 69 can be prevented. Accordingly,bonding wherein such joining strength between the electrodes 33 and 67as described above is maintained can be achieved.

Besides, the first insulating film 35 of the sensor substrate 2 side isconfigured from a diffusion preventing material with respect to thesecond electrode 67 of the circuit substrate 7 side, and the secondinsulating film 69 on the circuit substrate 7 side is configured from adiffusion preventing material with respect to the first electrode 33 ofthe sensor substrate 2 side. Consequently, mutual diffusion of anelectrode material between the sensor substrate 2 and the circuitsubstrate 7 can be prevented.

In addition, the bonding face 41 on the sensor substrate 2 side isconfigured only from the first electrodes 33 and the first insulatingfilm 35, and the bonding face 71 on the circuit substrate 7 side isconfigured only from the second electrodes 67 and the second insulatingfilm 69. Therefore, the bonding faces 41 and 71 are not configured froma barrier metal layer which is chemically inactive and is not likely tomaintain the joining strength, and the configuration of the bondingfaces is simplified. Also by this, the joining strength can bemaintained.

FIGS. 6A to 6C, 6A′ to 6C′ and 6D illustrate a fabrication procedure ofa semiconductor device of a comparative example. The procedure of thecomparative example illustrated in FIGS. 6A to 6D is carried out in thefollowing manner.

First, as seen in FIG. 6A, a groove pattern 101 a is formed on a firstinsulating film 101 which covers the surface of one of substrates and abarrier metal layer 102 for an electrode material is formed along thegroove pattern 101 a, whereafter a first electrode film 103 a made ofcopper (Cu) is formed on the barrier metal layer 102. Then, as seen inFIG. 6B, the first electrode film 103 a is flattened and removed by CMPto expose the barrier metal layer 102. Thereupon, CMP in which thebarrier metal layer 102 is used as a polishing stopper is carried out.Further, as this CMP, such CMP wherein polishing is automaticallystopped is carried out in order beginning with a portion of the firstelectrode film 103 a around which the barrier metal layer 102 is exposedto the polishing face.

Thereafter, as shown in FIG. 6C, the barrier metal layer 102 isflattened and removed by polishing to expose the first insulating film101. By the foregoing, a first electrode 103 in which the firstelectrode film 103 a made of copper (Cu) is embedded in the groovepattern 101 a of the first insulating film 101 with the barrier metallayer 102 interposed therebetween is formed.

Meanwhile, as shown in FIGS. 6A′ to 6C′, also on the surface side of theother substrate, a second electrode 203 in which a second electrode film203 a made of copper (Cu) is embedded with a barrier metal layer 202interposed therebetween is formed in a groove pattern 201 a of a secondinsulating film 201 by a similar procedure.

Thereafter, as shown in FIG. 6D, the substrates are disposed such thatthe polished faces thereof are opposed to each other and are joinedtogether at the first electrode 103 and the second electrode 203 thereoffacing each other to bond them to each other.

In such a procedure of the comparative example as just described, inpolishing of the barrier metal layer 102 and the first electrode film103 a in FIG. 6B to FIG. 6C, a sudden change in exposure area of thefirst electrode film 103 a made of copper (Cu) which is chemicallyactive does not occur. Therefore, CMP wherein polishing is automaticallystopped in order beginning with a portion of the first electrode film103 a around which the first insulating film 101 is exposed cannot becarried out. Accordingly, occurrence of dishing or erosion in thepolishing face cannot be prevented, and it is difficult to obtain a flatpolished face. This similarly applies also to the step illustrated inFIG. 6C′.

Accordingly, as seen in FIG. 6D, even if the polished faces which areinferior in flatness are opposed to each other to bond the substrates toeach other, sufficient bonding strength cannot be obtained. Besides,also the joining strength between the first electrode 103 and the secondelectrode 203 cannot be obtained sufficiently.

Further, the polished face shown in FIG. 6C is configured from the firstinsulating film 101, barrier metal layer 102 and first electrode 103.Meanwhile, also the polished face shown in FIG. 6C′ is configured fromthe second insulating film 201, barrier metal layer 202 and secondelectrode 203. Therefore, on a joining interface of the polished faces,also a joining interface between the first insulating film 101 and firstelectrode 103 and the barrier metal layer 202 and a joining interfacebetween the second insulating film 201 and second electrode 203 and thebarrier metal layer 102 are generated. However, since the barrier metallayers 102 and 202 are chemically inactive, pre-processing by a plasmaprocess or a wet process is difficult upon bonding. To this end, atportions of the bonding faces at which the barrier metal layers 102 and202 are exposed, high joining strength cannot be obtained. This makes afactor of inviting degradation of the bonding strength between thesubstrates.

In contrast with such a comparative example as described above, in thesemiconductor device of the present embodiment shown in FIG. 2, bondingis carried out between the flat bonding face 41 and the flat bondingface 71, simplified to two kinds, of the first electrode 33 and firstinsulating film 35 and the second electrode 67 and second insulatingfilm 69. Further, between the first electrode 33 and the secondelectrode 67, between the first insulating film 35 and the secondinsulating film 69, between the first electrode 33 and the secondinsulating film 69, and between the second electrode 67 and the firstinsulating film 35, sufficient joining strength can be obtained.Therefore, between the sensor substrate 2 which is a first substrate andthe circuit substrate 7 which is a second substrate, sufficient bondingstrength can be obtained.

6. Modification to the Semiconductor Device of the First Embodiment

FIG. 7 shows a semiconductor device 1′ according to a modification tothe first embodiment. Referring to FIG. 7, a first insulating film 35′including an interlayer insulating film 35-1 and a diffusion preventinginsulating film 35-2 may be provided on the sensor substrate 2 as afirst substrate. In this instance, a groove pattern 35 a is provided inthe interlayer insulating film 35-1 made of, for example, silicon oxideor a low dielectric material, and the diffusion preventing insulatingfilm 35-2 is provided in a state in which it covers the interlayerinsulating film 35-1 including an inner face of the groove pattern 35 a.Further, a first electrode 33 is provided in the groove pattern 35 awith the diffusion preventing insulating film 35-2 interposedtherebetween. Consequently, the periphery of the first electrode 33 issurrounded by the diffusion preventing insulating film 35-2, and abonding face 41 is configured from the first electrode 33 and thediffusion preventing insulating film 35-2.

Also on the circuit substrate 7 as a second substrate, a secondinsulating film 69′ including an interlayer insulating film 69-1 and adiffusion preventing insulating film 69-2 may be provided similarly.Consequently, the periphery of the second electrode 67 is surrounded bythe diffusion preventing insulating film 69-2, and a bonding face 71 isconfigured from the second electrode 67 and the diffusion preventinginsulating film 69-2.

Also with the semiconductor device 1′ having such a configuration asdescribed above, the bonding face 41 of the sensor substrate 2 and thebonding face 71 of the circuit substrate 7 can be configured only fromthe diffusion preventing insulating films 35-2 and 69-2 and theelectrodes 33 and 67 to assure joining strength. Besides, diffusion ofmaterials configuring the electrodes 33 and 67 into the interlayerinsulating films 35-1 and 69-1 can be prevented.

As a result, in the semiconductor device 1′ of a three-dimensionalstructure wherein the first electrode 33 and the second electrode 67 arejoined together by bonding of the two substrates 2 and 7, bondingstrength is assured while diffusion of an electrode material isprevented. Consequently, improvement in reliability can be achieved.

Further, in fabrication of the semiconductor device 1′ having such aconfiguration as described above, when the sensor substrate 2 which is afirst substrate is produced, the film which configures the firstelectrode 33 may be polished by CMP using the diffusion preventinginsulating film 35-2 as a stopper. Therefore, the point of time at whichthe diffusion preventing insulating film 35-2 is exposed can be detectedaccurately as an end point of polishing, and CMP can be ended withoutgeneration of dishing to obtain a flat polished face as the bonding face41.

Also in the case where the circuit substrate 7 which is a secondsubstrate is to be produced, a film which configures the secondelectrode 67 may be polished by CMP using the diffusion preventinginsulating film 69-2 as a stopper similarly. Therefore, a flat polishedface can be obtained as the bonding face 71 similarly.

As a result, similarly as in the fabrication method of the firstembodiment described above, bonding wherein the bonding face 41 and thebonding face 71 are joined together over the overall area is carriedout, and bonding strength between the sensor substrate 2 and the circuitsubstrate 7 can be maintained. Besides, the diffusion preventinginsulating film 35-2 of the sensor substrate 2 side may be configuredfrom a diffusion preventing material with respect to the secondelectrode 67 of the circuit substrate 7 side, and the diffusionpreventing insulating film 69-2 of the circuit substrate 7 side may beconfigured from a diffusion preventing material with respect to thefirst electrode 33 of the sensor substrate 2 side. Consequently, alsodiffusion of an electrode material between the sensor substrate 2 andthe circuit substrate 7 can be prevented. In addition, the bonding face41 of the sensor substrate 2 side is configured only from the firstelectrode 33 and the diffusion preventing insulating film 35-2, and thebonding face 71 of the circuit substrate 7 side is configured only fromthe second electrode 67 and the diffusion preventing insulating film69-2. Therefore, the configuration of the bonding face is simplified,and also by this, joining strength can be maintained.

Second Embodiment 1. Configuration of the Semiconductor Device of theSecond Embodiment

FIG. 8 shows a partial sectional configuration of a semiconductor deviceaccording to a second embodiment of the present disclosure. In thefollowing, a detailed configuration of the semiconductor device of thepresent embodiment is described with reference to FIG. 8.

The semiconductor device 301 shown in FIG. 8 is a solid-state imagepickup device of a three-dimensional structure wherein a first substrate302 and a second substrate 307 are bonded to each other such that abonding face 341 of the first substrate 302 and a bonding face 371 ofthe second substrate 307 are disposed in an opposing relationship toeach other in a state in which an insulating thin film 312 is sandwichedtherebetween. In the present embodiment, the semiconductor device 301 ischaracterized in the structure that the first substrate 302 and thesecond substrate 307 are bonded to each other with the insulating thinfilm 312 interposed therebetween.

The first substrate 302 includes a semiconductor layer 302 a, a wiringline layer 302 b and an electrode layer 302 c laminated in order fromthe opposite side to the second substrate 307. The surface of theelectrode layer 302 c is configured as a bonding face 341 to the secondsubstrate 307. Meanwhile, the second substrate 307 includes asemiconductor layer 307 a, a wiring line layer 307 b and an electrodelayer 307 c laminated in order from the opposite side to the firstsubstrate 302. The surface of the electrode layer 307 c is configured asa bonding face 371 to the first substrate 302.

On the face of the first substrate 302 on the opposite side to thesecond substrate 307, a protective film 315, a color filter layer 317and an on-chip lenses 319 are laminated in the order as shown in FIG. 8.

Now, a detailed configuration of the layers which configure the firstsubstrate 302 and the second substrate 307 and the insulating thin film312 is described successively, and then a configuration of theprotective film 315, color filter layer 317 and on-chip lenses 319 isdescribed successively.

[Semiconductor Layer 302 a (First Substrate 302 Side)]

The semiconductor layer 302 a of a first substrate 302 is a thin film ofthe semiconductor substrate 320 made of, for example, single crystalsilicon. On the first face side of the semiconductor layer 302 a onwhich the color filter layer 317, on-chip lenses 319 and so forth aredisposed, a photoelectric conversion portion 321 formed, for example,from an n-type impurity or a p-type purity is provided for each pixel.Meanwhile, on the second face of the semiconductor layer 302 a, afloating diffusion FD and a source/drain region 323 of a transistor Trformed from an n+-type impurity layer as well as other impurity layersand so forth not shown are provided.

[Wiring Line Layer 302 b (First Substrate 302 Side)]

The wiring line layer 302 b provided on the semiconductor layer 302 a ofthe first substrate 302 has, on an interface side thereof with thesemiconductor layer 302 a, a transfer gate TG and a gate electrode 327of the transistor Tr as well as other electrodes not shown provided witha gate insulating film 325 interposed therebetween. The transfer gate TGand the gate electrode 327 are covered with an interlayer insulatingfilm 329, and an embedded wiring line 331 is provided in a groovepattern formed on the interlayer insulating film 329. The embeddedwiring line 331 is configured from a barrier metal layer 331 a whichcovers the inner wall of the groove pattern, and a wiring line layer 331b made of copper (Cu) and embedded in the groove pattern with thebarrier metal layer 331 a interposed therebetween.

It is to be noted that such a wiring line layer 302 b as described abovemay be configured further as a laminated multilayer wiring line layer.

[Electrode Layer 302 c (First Substrate 302 Side)]

The electrode layer 302 c provided on the wiring line layer 302 b of thefirst substrate 302 includes, on the interface side with the wiring linelayer 302 b, a diffusion preventing insulating film 332 for copper (Cu)and a first insulating film 335 laminated on the diffusion preventinginsulating film 332. The first insulating film 335 is formed, forexample, from a TEOS film, and a first electrode 333 as an embeddedelectrode is provided in the groove pattern formed on the firstinsulating film 335. It is to be noted that the TEOS film is a siliconoxide film formed by a chemical vapor deposition method (hereinafterreferred to as CVD method) wherein TEOS gas (Tetra Ethoxy Silane gas:composition Si(OC2H5)4) as source gas. The first electrode 333 isconfigured from a barrier metal layer 333 a which covers the inner wallof the groove pattern, a first electrode film 333 b made of copper (Cu)and embedded in the groove pattern with the barrier metal layer 333 ainterposed therebetween.

The surface of the electrode layer 302 c having such a configuration asdescribed above is used as a bonding face 341 on the first substrate 302side to the second substrate 307. The bonding face 341 is configuredsuch that the first electrode 333 and the first insulating film 335 areexposed thereto and is in a state flattened, for example, by chemicalmechanical polishing (hereinafter referred to as CMP).

It is to be noted that, though not shown in FIG. 8, the groove patternprovided in the first insulating film 335 partly extends to the embeddedwiring line 331 provided in the wiring line layer 302 b, and the firstelectrode 333 embedded in the groove pattern is in a state connected tothe embedded wiring line 331 as occasion demands.

[Semiconductor Layer 307 a (Second Substrate 307 Side)]

Meanwhile, the semiconductor layer 307 a of the second substrate 307 isformed from a thin film of a semiconductor substrate 350 made of, forexample, single crystal silicon. On the surface layer of thesemiconductor layer 307 a on the first substrate 302 side, asource/drain 351 of the transistor Tr and impurity layers not shown areprovided.

[Wiring Line Layer 307 b (Second Substrate 307 Side)]

The wiring line layer 307 b provided on the semiconductor layer 307 a ofthe second substrate 307 has, on the interface side thereof with thesemiconductor layer 307 a, a gate electrode 355 provided with a gateinsulating film 353 interposed therebetween and other electrodes notshown. The gate electrode 355 and the other electrodes are covered withan interlayer insulating film 357, and an embedded wiring line 359 isprovided in a groove pattern formed on the interlayer insulating film357. The embedded wiring line 359 is configured from a barrier metallayer 359 a which covers the inner wall of the groove pattern, and awiring line layer 359 b made of copper (Cu) and embedded in the groovepattern with the barrier metal layer 359 a interposed therebetween.

It is to be noted that such a wiring line layer 307 b as described abovemay have a multilayer wiring line layer structure.

[Electrode Layer 307 c (Second Substrate 307 Side)]

The electrode layer 307 c provided on the wiring line layer 307 b of thesecond substrate 307 includes, on the interface side thereof with thewiring line layer 307 b, a diffusion preventing insulating film 361 withrespect to copper (Cu) and a second insulating film 369 laminated on thediffusion preventing insulating film 361. The second insulating film 369is formed, for example, from a TEOS film, and a second electrode 367 asan embedded electrode is provided in a groove pattern formed in thesecond insulating film 369. The second electrode 367 is configured froma barrier metal layer 367 a which covers the inner wall of the groovepattern, and a second electrode film 367 b made of copper (Cu) andembedded in the groove pattern with the barrier metal layer 367 ainterposed therebetween. The second electrode 367 is disposed so as tocorrespond to the first electrode 333 of the first substrate 302 sideand is electrically connected to the first electrode 333 on the firstsubstrate 302 side with the insulating thin film 312 interposedtherebetween.

The surface of such an electrode layer 307 c as described above isformed as the bonding face 371 on the second substrate 307 to the firstsubstrate 302. The bonding face 371 is configured such that the secondelectrode 367 and the second insulating film 369 are exposed thereto andis in a state flattened, for example, by CMP.

[Insulating Thin Film 312]

The insulating thin film 312 is sandwiched between the bonding face 341of the first substrate 302 side and the bonding face 371 on the secondsubstrate 307 side and covers the overall area of the bonding face 341and the bonding face 371. In other words, the first substrate 302 andthe second substrate 307 are bonded to each other with the insulatingthin film 312 interposed therebetween.

Such an insulating thin film 312 as described above is formed, forexample, from an oxide film and a nitride film, and an oxide film and anitride film which are used popularly with semiconductors are used forthe insulating thin film 312. In the following, a component material ofthe insulating thin film 312 is described in detail.

In the case where the insulating thin film 312 is formed from an oxidefilm, for example, silicon oxide (SiO2) or hafnium oxide (HfO2) is used.In the case where the insulating thin film 312 is formed from an oxidefilm and the first electrode 333 and the second electrode 367 are madeof copper (Cu), copper (Cu) which is an electrode material for them isliable to diffuse into the insulating thin film 312. Since the electricresistance of the insulating thin film 312 decreases by such diffusionof copper (Cu), the dielectric between the first electrode 333 and thesecond electrode 367 with the insulating thin film 312 interposedtherebetween enhances. Therefore, in the case where the insulating thinfilm 312 is formed from an oxide film, the insulating thin film 312 maybe formed rather thick.

In the case where the insulating thin film 312 is formed from a nitridefilm, for example, silicon nitride (SiN) is used. The insulating thinfilm 312 formed from a nitride film has a diffusion preventing propertywith respect to the first electrode 333 and the second electrode 367.

Consequently, within the same substrate, leak current which appearsbetween electrodes of the same substrate through the insulating thinfilm 312 can be prevented. In other words, in the first substrate 302,leak current between adjacent first electrodes 333 which appears throughthe insulating thin film 312 can be prevented. Similarly, in the secondsubstrate 307, leak current between adjacent second electrodes 367 whichappears through the insulating thin film 312 can be prevented.

On the other hand, between different substrates, diffusion of anelectrode material into an insulating film on the opposing electrodeside can be prevented. In other words, diffusion of the first electrode333 on the first substrate 302 side into the second insulating film 369on the opposing second substrate 307 side can be prevented. Similarly,diffusion of the second electrode 367 on the second substrate 307 sideinto the first insulating film 335 on the opposing first substrate 302side can be prevented. Therefore, it is not necessary to provide abarrier film made of a diffusion preventing material with respect to anelectrode of the opposite electrode side at a portion of each of thebonding faces of the substrates at which an insulating film is exposed.

Further, particularly in the present embodiment, it is important thatthe first electrode 333 of the first substrate 302 side and the secondelectrode 367 of the second substrate 307 side are electricallyconnected to each other with the insulating thin film 312 interposedtherebetween. Therefore, the thickness of the insulating thin film 312is very small. The film thickness of the insulating thin film 312differs depending upon the material of the insulating thin film 312 andis equal to or smaller than approximately 2 nm, for example, with regardto oxides such as silicon oxide (SiO2) and hafnium oxide (HfO2) andalmost all of the other materials. However, depending upon the filmquality of the insulating thin film 312, a further thicker film may beused. Between the first electrode 333 and the second electrode 367disposed in an opposing relationship with the insulating thin film 312interposed therebetween, tunnel current flows. Further, if a voltageequal to or higher than a fixed level is applied to cause breakdown,then the first electrode 333 and the second electrode 367 are placedinto a fully conducting state therebetween and current flows betweenthem.

It is to be noted that, in the semiconductor device 301 of the presentembodiment, the insulating thin film 312 may not necessarily have aone-layer structure described hereinabove but may have a laminatedstructure of the same material or a laminated structure of differentmaterials.

[Protective Film 315, Color Filter Layer 317 and on-Chip Lenses 319]

The protective film 315 is provided covering the photoelectricconversion portion 321 of the first substrate 302. The protective film315 is configured from a material film having a passivation property,and, for example, a silicon oxide film, a silicon nitride film, asilicon oxynitride film or a like film is used for the protective film315.

The color filter layer 317 is configured from color filters of differentcolors provided in a one-by-one corresponding relationship to thephotoelectric conversion portions 321. The array of the color filters ofthe colors is not limited particularly.

The on-chip lenses 319 are provided in a one-by-one correspondingrelationship to the photoelectric conversion portions 321 and the colorfilters of the different colors which configure the color filter layer317 and are configured such that incident light is condensed at thephotoelectric conversion portions 321.

[Effects by the Configuration of the Semiconductor Device of the PresentEmbodiment]

In the semiconductor device 301 of the present embodiment configured insuch a manner as described above, since the first substrate 302 and thesecond substrate 307 are bonded to each other with the insulating thinfilm 312 interposed therebetween as seen in FIG. 8, the bonding face 341of the first substrate 302 and the bonding face 371 of the secondsubstrate 307 do not directly contact with each other. Accordingly,generation of voids which are normally generated, in the configurationwherein the bonding faces of them are joined directly to each other,along the joining interface is prevented. Consequently, with thesemiconductor device, the joining strength between the two substrates isincreased and enhancement of the reliability is achieved.

Particularly in the case where the first insulating film 335 and thesecond insulating film 369 are formed from a TEOS film, since many OHgroups exist on the surface of the TEOS film, voids by dehydrationcondensation are generated along the joining interface along which theinsulating films each in the form of a TEOS film contact are jointeddirectly with each other. Also in the case where an insulating film is aTEOS film, since, in the semiconductor device 301 of the presentembodiment, substrates are bonded to each other with the insulating thinfilm 312 interposed therebetween, the TEOS films are not joined directlyto each other, and generation of voids by dehydration condensation canbe prevented. Consequently, with the semiconductor device, the joiningstrength between the two substrates increases and enhancement of thereliability is achieved.

2. Production Procedure of the First Substrate (Sensor Substrate) inFabrication of the Semiconductor Device of the Second Embodiment

FIGS. 9A to 9E illustrate a production procedure of a first substrate302 for use with fabrication of the semiconductor device of the secondembodiment. In the following, a production procedure of the firstsubstrate 302 as a sensor substrate used in the present embodiment isdescribed with reference to FIGS. 9A to 9E.

A semiconductor substrate 320 made of, for example, single crystalsilicon is prepared as shown in FIG. 9A. A photoelectric conversionportion 321 made of an n-type impurity layer is formed at apredetermined depth of the semiconductor substrate 320, and then acharge transfer portion formed from an n+ type impurity layer and acharge accumulation portion for holes formed from a p+ type impuritylayer are formed on a surface layer of the photoelectric conversionportion 321. A floating diffusion FD, a source/drain 323 and a furtherimpurity layer not shown formed from an n+ type impurity layer is formedfor each pixel on the surface layer of the semiconductor substrate 320.

Then, a gate insulating film 325 is formed on the surface of thesemiconductor substrate 320, and a transfer gate TG and a gate electrode327 are formed on the gate insulating film 325. The transfer gate TG isformed between the floating diffusion FD and the photoelectricconversion portion 321, and the gate electrode 327 is formed between thesource/drain 323. Further, at the same step, also other electrodes notshown are formed.

It is to be noted that the steps described may be carried out in anordinary production procedure selected suitably.

Thereafter, an interlayer insulating film 329 made of, for example,silicon oxide is formed on the gate insulating film 325 in a state inwhich it covers the transfer gates TG and the gate electrodes 327.Further, for each pixel a groove pattern is formed in the interlayerinsulating film 329, and an embedded wiring line 331 in which a wiringline layer 331 b is embedded with a barrier metal layer 331 a interposedtherebetween is formed in the groove pattern. The embedded wiring lines331 are formed such that they connect to the transfer gates TG atnecessary places. Further, though not shown, some of the embedded wiringline 331 are formed in contact with the sources/drains 23. As a result,a wiring line layer 302 b including the embedded wiring lines 331 isobtained. It is to be noted that, for the formation of the embeddedwiring lines 331, an embedded wiring technique hereinafter describedwith reference to FIG. 9B and so forth is applied.

Then, a diffusion preventing insulating film 332 is formed on the wiringline layer 302 b, and a first insulating film 335 is formed on thediffusion preventing insulating film 332. For example, a CVD method inwhich TEOS (tetraethylorthosilicate) gas is used is applied to form thefirst insulating film 335 formed from a TEOS film. Thereafter, firstelectrodes 333 are formed on the first insulating film 335 applying anembedded wiring technique described below.

A groove pattern 335 a is formed for each pixel on the first insulatingfilm 335 as shown in FIG. 9B. Though not shown, the groove pattern 335 ais formed in a shape in which it extends to the embedded wiring line 331at a necessary place.

As shown in FIG. 9C, a barrier metal layer 333 a is formed in a state inwhich it covers the inner wall of the groove pattern 335 a, and a firstelectrode film 333 b is formed on the barrier metal layer 333 a in astate in which the groove pattern 335 a is embedded. The barrier metallayer 333 a is configured from a material having a barrier property withwhich the first electrode film 333 b diffuses into the first insulatingfilm 335 while the first electrode film 333 b is made of copper (Cu).However, the material of the first electrode film 333 b is not limitedto this, but the first electrode film 333 b may be configured from aconductive material.

As shown in FIG. 9D, the first electrode film 333 b is flattened andremoved by a CMP method until the barrier metal layer 333 a is exposed,and the barrier metal layer 333 a is flattened and removed until thefirst insulating film 335 is exposed. By this, the first electrode 333in which the first electrode film 333 b is embedded with the barriermetal layer 333 a interposed therebetween is formed in the groovepattern 335 a. As a result, an electrode layer 302 c including the firstelectrodes 333 is obtained.

By the steps described above, the first substrate 302 having a flatbonding face 341 to which the first electrodes 333 and the firstinsulating film 335 are exposed is produced as a sensor substrate. It isto be noted that, as occasion demands, pre-processing by a wet processor a plasma process is carried out for the bonding face 341.

The foregoing steps may be carried out in an ordinary step order, andthe step procedure is not restricted particularly but the steps may becarried out in a suitable order. In the present technology, thefollowing formation of an insulating thin film is a characteristic step.

[Formation Step of the Insulating Thin Film]

As shown in FIG. 9E, an insulating thin film 312 a is formed by anatomic layer deposition method (hereinafter referred to as ALD method)in a state in which it covers the overall area of the bonding face 341of the first substrate 302.

An outline of a procedure of the ALD method is described.

First, a first reactant and a second reactant which contain componentelements of a thin film to be formed are prepared. As a film formationstep, a first step at which gas containing the first reactant issupplied to a substrate so as to be absorbed by the substrate and asecond step at which gas containing the second reactant is supplied soas to be absorbed by the substrate are carried out. Further, between thesteps, inert gas is supplied to purge unabsorbed reactant. By carryingout the film formation step by one cycle, one atomic layer isaccumulated, and by repeating the film formation cycle, a film of adesired thickness is obtained. It is to be noted that any one of thefirst and second steps may be carried out first.

Such a film formation method as described above is the ALD method andhas such characteristics as described below.

The ALD method is a method of repeating a cycle of the film formationstep to form a film. By adjustment of the number of cycles, formation ofa film whose film thickness is controlled with a high degree of accuracyin a unit of an atomic layer can be carried out. If such an ALD methodas just described is applied to formation of the insulating thin film312 a, then even if the insulating thin film 312 a is very thin, it canbe formed with high film thickness controllability.

Further, the ALD method is a method by which a film can be formed by alow temperature process at a temperature lower than approximately 500°C. Since the electrode layer 302 c is formed already upon formation ofthe insulating thin film 312 a, the heat resisting property of a metalwhich configures the electrode layer 302 c is taken into consideration,and for the formation of the insulating thin film 312 a, a lowtemperature process is demanded. Therefore, if such an ALD method isapplied to formation of the insulating thin film 312 a, then theinsulating thin film 312 a can be formed without deterioration of theelectrode layer 302 c by the low temperature process.

The ALD method is a method of depositing one by one atomic layer to forma film as described hereinabove. If such an ALD method is applied toformation of the insulating thin film 312 a, then the overall area ofthe bonding face 341 can be covered with the flat and uniform insulatingthin film 312 without deteriorating the flatness of the substratesurface flattened very much by CMP.

In the following, film formation conditions by the ALD method of theinsulating thin film 312 a formed from an oxide film or a nitride filmis described particularly as an example.

In the case where the insulating thin film 312 a is formed from an oxidefilm such as a film of SiO2 or HfO2, a Si containing reactant or a Hfcontaining reactant is used as the first reactant while an O containingreactant is used as the second reactant in the ALD method describedabove. Steps at which the reactants are supplied for an absorptionreaction are carried out alternately to form an insulating thin film 312a formed from an oxide film of SiO2 or HfO2 on the bonding face 341.Here, as the Si containing reactant, a substance which can be suppliedin the form of gas such as silane (SiH4) or dichlorosilane (H2SiCl2) isused. As the Hf containing reactant, tetrakis dimethyl amino hafnium(Hf[N(CH3)2]4) or the like is used. As the O containing reactant, watervapor gas, ozone gas or the like is used.

On the other hand, in the case where the insulating thin film 312 a isformed from a nitride film (SiN) or the like, a Si containing reactantis used as the first reactant while a N containing reactant is used asthe second reactant in the ALD method described hereinabove. Byalternately repeating steps at which such reactants are supplied for anabsorption reaction, an insulating thin film 312 a formed from a nitridefilm (SiN) is formed on the bonding face 341. Here, as the N containingreactant, for example, nitrogen gas, ammonia gas or the like is used. Asthe O containing reactant, water vapor gas, ozone gas or the like isused.

By the foregoing process, a very thin and uniform insulating thin film312 a is formed on the first substrate 302 in such a state as to coverthe overall area of the bonding face 341.

3. Production Procedure of the Second Substrate (Circuit Substrate) inFabrication of the Semiconductor Device of the Second Embodiment

FIGS. 10A and 10B illustrate a production procedure of a secondsubstrate 307 used for fabrication of the semiconductor device of thesecond embodiment described hereinabove. In the following, a productionprocedure of the second substrate or circuit substrate 307 used in thesecond embodiment is described with reference to FIGS. 10A and 10B.

As shown in FIG. 10A, a semiconductor substrate 350 made of, forexample, single crystal silicon is prepared. On a surface layer of thesemiconductor substrate 350, a source/drain 351 of individual conductivetypes and other impurity layers not shown are formed for each pixel. Asemiconductor layer 307 a is obtained thereby.

Then, a gate insulating film 353 is formed on the semiconductor layer307 a, and a gate electrode 355 is formed on the gate insulating film353. The gate electrode 355 is formed between the source/drain 351.Further, at the same step, the other electrodes not shown are formed.

Then, an interlayer insulating film 357 made of, for example, siliconoxide is formed on the gate insulating film 353 in such a state as tocover the gate electrode 355. An embedded wiring line 359 in which awiring line layer 359 b is embedded with a barrier metal layer 359 ainterposed therebetween is formed in the groove pattern of theinterlayer insulating film 357 to obtain a wiring line layer 307 b whichincludes the embedded wiring line 359. The formation of the embeddedwiring line 359 here is carried out applying the embedded wiringtechnique similarly to the formation of the first electrodes 333described hereinabove.

Thereafter, a second insulating film 369 formed, for example, from aTEOS film is deposited to form a film on the wiring line layer 307 bwith a diffusion preventing insulating layer 361 interposedtherebetween. Consequently, a second electrode 367 in which a secondelectrode film 367 b is embedded with a barrier metal layer 367 ainterposed therebetween is formed in each groove pattern of the secondinsulating film 369 thereby to obtain an electrode layer 307 c whichincludes the second electrode 367. The formation of the second electrode367 here is carried out similarly to the formation of the firstelectrodes 333 described hereinabove.

By the steps described above, a second substrate 307 having a flatbonding face 371 to which the second electrode 367 and the secondinsulating film 369 are exposed is produced as a circuit substrate.

The steps described above may be carried out in an ordinary stepprocedure, and the step procedure is not limited to a special stepprocedure and the steps can be carried out in a suitable procedure. Inthe present technology, formation of an insulating thin film and bondingof substrates described below are characteristic steps.

As shown in FIG. 10B, an insulating thin film 312 b is formed by an ALDmethod on the bonding face 371 similarly as in the formation of theinsulating thin film 312 a on the first substrate 302 side.

Consequently, the very thin and uniform insulating thin film 312 b isformed on the second substrate 307 in such a state as to cover theoverall area of the bonding face 371. It is to be noted that theinsulating thin film 312 b may be a film same as or different from theinsulating thin film 312 a on the first substrate 302 side.

4. Bonding Procedure of the Substrates in Fabrication of theSemiconductor Device of the Second Embodiment

A bonding procedure of the first substrate 302 wherein the insulatingthin film 312 a is formed on the bonding face 341 and the secondsubstrate 307 wherein the insulating thin film 312 b is formed on thebonding face 371 is described with reference to FIGS. 11A and 11B.

The bonding face 341 of the first substrate 302 and the bonding face 371of the second substrate 307 are disposed in an opposing relationship toeach other with an insulating thin film interposed therebetween as shownin FIG. 11A, and then are positioned such that the first electrodes 333of the first substrate 302 and the second electrodes 367 of the secondsubstrate 307 correspond to each other. While the example shownillustrates a state in which the first electrodes 333 and the secondelectrodes 367 correspond in a 1:1 corresponding relationship to eachother, the corresponding relationship is not limited to this.

As shown in FIG. 11B, the first substrate 302 and the second substrate307 are subjected to heat treatment in a state in which the insulatingthin film 312 a of the first substrate 302 and the insulating thin film312 b on the second substrate 307 are opposed to each other to join theinsulating thin film 312 a and the insulating thin film 312 b to eachother. Such heat treatment is carried out at a temperature and for aperiod of time sufficient to allow the insulating thin films 312 to bejoined together sufficiently within a range within which no influence ishad on the elements or the wiring lines formed on the first substrate302 and the second substrate 307.

For example, in the case where the first electrodes 333 and the secondelectrodes 367 are configured using materials which contain copper (Cu)as a principal component, heat treatment is carried out at 200 to 600°C. for approximately one to five hours. Such heat treatment may becarried out under a pressurized atmosphere or may be carried out in astate in which the first substrate 302 and the second substrate 307 arepressed to each other from the opposite face sides thereof. As anexample, heat treatment at 400° C. for four hours is carried out tocarry out connection between the first electrodes 333 and the secondelectrodes 367 with the insulating thin films 312 interposedtherebetween. Consequently, the insulating thin film 312 a and theinsulating thin film 312 b are joined together while the first substrate302 and the second substrate 307 are bonded to each other.

Here, in the case where the insulating thin films 312 a and 312 b areformed on the bonding faces 341 and 371 of both of the first substrate302 and the second substrate 307 as described above, the insulating thinfilms 312 a and 312 b may be configured from a same material or frommaterials different from each other.

It is to be noted that, in the fabrication method of the semiconductordevice of the present embodiment, an insulating thin film may be formedonly on the bonding face of one of the first substrate 302 and thesecond substrate 307. For example, the insulating thin film 312 a may beformed only on the bonding face 341 of the first substrate 302 such thatthe first substrate 302 and the second substrate 307 are bonded to eachother by joining between the insulating thin film 312 a of the firstsubstrate 302 side and the bonding face 371 of the second substrate 307side.

After the first substrate 302 and the second substrate 307 are bonded toeach other as described above, the semiconductor substrate 320 of thefirst substrate 302 side is thinned into the semiconductor layer 302 ato expose the photoelectric conversion portion 321. Further, as occasiondemands, the semiconductor substrate 350 may be thinned on thesemiconductor layer 307 a of the second substrate 307 side.

Thereafter, a protective film 315 is formed on the exposed face of thephotoelectric conversion portion 321 of the first substrate 302, and acolor filter layer 317 and on-chip lenses 319 are formed on theprotective film 315 to complete a semiconductor device 1 or asolid-state image pickup device.

[Effect by the Fabrication Method of the Semiconductor Device of theSecond Embodiment]

In such a fabrication method of the semiconductor device of the presentembodiment as described above, the insulating thin films 312 a and 312 bare formed on the first substrate 302 and the second substrate 307 andthe first substrate 302 and the second substrate 307 are bonded to eachother by joining the faces of the first substrate 302 and the secondsubstrate 307 on which the insulating thin films 312 a and 312 b areformed, respectively. Therefore, in comparison with an alternative casein which the bonding faces 341 and 371 flattened by the CMP are joineddirectly to each other, the semiconductor device 1 in the presentembodiment wherein the first substrate 302 and the second substrate 307are bonded to each other by the joining of the faces thereof on whichthe insulating thin films 312 a and 312 b are formed, respectively, issuperior in joining property. It is to be noted that, also in the casewhere the insulating thin film 312 a is formed only on the bonding face341 of the first substrate 302, the insulating thin film 312 a of thefirst substrate 302 side and the bonding face 371 of the secondsubstrate 307 side are joined together, and the joining property of thesubstrates is better than that in the alternative case in which thebonding faces 341 and 371 are joined directly to each other.

For example, there is the possibility that the first insulating film 335and the second insulating film 369 which configure the bonding faces 341and 371 flattened by the CMP may contain water at the CMP step. Further,if the first insulating film 335 and the second insulating film 369which configure the bonding faces 341 and 371 are formed from a TEOSfilm, then the first insulating film 335 and the second insulating film369 are formed as films originally having a high moisture content due tothe formation conditions of the TEOS film. Accordingly, in the casewhere the bonding faces 341 and 371 containing water in this manner areto be joined directly to each other, in heat treatment after thebonding, outgoing gas is concentrated on the joining interface to formvoids. However, in the present embodiment, since the insulating thinfilms 312 a and 312 b cover over the overall area of the bonding faces341 and 371, it is possible to prevent outgoing gas from beingconcentrated on the joining interface thereby to suppress generation ofvoids.

Especially, in the case where the insulating thin film 312 a on thebonding face 341 of the first substrate 302 and the insulating thin film312 b on the bonding face 371 of the second substrate 307 are configuredfrom films of the same material, since the same material films arejoined to each other, firmer joining can be achieved. Consequently, asemiconductor device which is enhanced in joining strength of thesubstrates and hence in reliability can be obtained.

Further, by using the ALD method to form the insulating thin films 312 aand 312 b, also the following advantages can be achieved.

First, since the ALD method is a method which is good in film thicknesscontrollability by film formation in a unit of an atomic layer.Consequently, even with a structure wherein the first electrodes 333 ofthe first substrate 302 side and the second electrode 367 of the secondsubstrate 307 are disposed in an opposing relationship to each otherwith the insulating thin film 312 interposed therebetween, since theinsulating thin film 312 is a very thin film, electric connectionbetween the first electrodes 333 and the second electrodes 367 ispermitted.

Further, since the ALD method is a method which is good in filmthickness uniformity due to film formation in a unit of an atomic layer,the uniform insulating thin films 312 a and 312 b are formed on thefirst substrate 302 and the second substrate 307, respectively,maintaining the flatness of the bonding faces 341 and 371 flattened byCMP. Since joining between the flattened joining faces of the insulatingthin films 312 a and 312 b formed is achieved, the resulting joining issuperior in close contactness, and joining of the substrates which isimproved in joining strength can be anticipated.

Further, since the ALD method uses a low temperature process to form afilm, the insulating thin films 312 a and 312 b can be formed on theelectrode layer 302 c of the first substrate 302 side and the electrodelayer 307 c of the second substrate 307 side without suffering fromdeterioration of the metals of the electrode layer 302 c of the firstsubstrate 302 side and the electrode layer 307 c of the second substrate307 by high heat.

Finally, since the ALD method is a film formation method in a unit of anatomic layer, the insulating thin films 312 a and 312 b formed are finefilms and have a very low moisture content. Therefore, since the formedjoining faces of the insulating thin films 312 a and 312 b having a lowmoisture content are joined together, there is no possibility that voidsmay appear on the joining face.

Consequently, a semiconductor device wherein the joining strength of thesubstrates increases to achieve enhancement of the reliability.

Third Embodiment 1. First Working Example Problems of a Cu—Cu JoiningTechnology in Related Art

Before a semiconductor device according to a first working example of athird embodiment of the present disclosure is described, problems whichmay possibly occur with a Cu—Cu joining technique in related art aredescribed with reference to FIGS. 12A, 12B and 13. FIG. 12A shows ageneral configuration of semiconductor members before two semiconductormembers are joined together, and FIG. 12B shows a general cross sectionof the two semiconductor members after joined in the proximity of ajoining interface. Further, FIG. 13 illustrates problems which may occurin the case where joining misalignment occurs upon bonding of the twosemiconductor members.

In FIGS. 12A, 12B and 13, an example is shown wherein a firstsemiconductor member 610 including a first SiO2 layer 611, a first Cuelectrode 612 and a first Cu barrier layer 613 and a secondsemiconductor member 620 including a second SiO2 layer 621, a second Cuelectrode 622 and a second Cu barrier layer 623 are joined together.

It is to be noted that, in the example shown in FIGS. 12A and 12B, theCu electrodes are formed in an embedded manner on one surface of theSiO2 layer of the semiconductor members. In particular, the Cuelectrodes are formed such that they are exposed to the one surface ofthe SiO2 layer and the exposed face is substantially in flush with theone surface of the SiO2 layer. Further, each Cu barrier layer isprovided between a Cu electrode and a SiO2 layer. Further, the surfaceof the first semiconductor member 610 on the first Cu electrode 612 sideand the surface of the second semiconductor member 620 on the second Cuelectrode 622 side are bonded to each other.

When the first semiconductor member 610 and the second semiconductormember 620 are bonded to each other, if joining misalignment occursbetween them, then a contact region between a Cu electrode of one of thesemiconductor members and a SiO2 layer of the other semiconductor memberis generated on a joining interface Sj as seen in FIG. 12B.

In this instance, there is the possibility that, by an annealing processor the like upon joining, Cu 630 may diffuse from the Cu electrodes intothe SiO2 layers until the adjacent Cu electrodes are short-circuited onthe joining interface Sj as seen in FIG. 13. Further, if the diffusionamount of the Cu 630 from the Cu electrodes into the SiO2 layers isgreat, then since the amount of Cu in the Cu electrodes decreases, forexample, such a failure as an increase of the contact resistance or afailure in conduction occurs may occur.

If such a failure in electric characteristic on the joining interface Sjas described above occurs, then the performance of the semiconductordevice is deteriorated. Therefore, in the present working example, theconfiguration of a semiconductor device which can eliminate suchfailures in electric characteristic on the joining interface Sj asdescribed above is described.

[Configuration of the Semiconductor Device]

FIGS. 14 and 15 show a general configuration of the semiconductor deviceaccording to the first working example. In particular, FIG. 14 shows ageneral cross section of the semiconductor device of the first workingexample in the proximity of a joining interface, and FIG. 15 shows aschematic top plan in the proximity of the joining interface andillustrates an arrangement relationship between Cu joining portions andan interface Cu barrier film hereinafter described. It is to be notedthat, in FIGS. 14 and 15, in order to simplify description, aconfiguration of only one joining interface is shown.

Referring first to FIG. 14, a semiconductor device 401 shown includes afirst semiconductor member 410 which is a first semiconductor sectionand a second semiconductor member 420 which is a second semiconductorsection. Further, in the semiconductor device 401 of the present workingexample, the first semiconductor member 410 is joined at a face thereofon a first interlayer insulating film 415 side to a face of the secondsemiconductor member 420 on an interface Cu barrier film 428 sidehereinafter described.

The first semiconductor member 410 includes a first semiconductorsubstrate not shown, a first SiO2 layer 411, a first Cu wiring lineportion 412, a first Cu barrier film 413, a first Cu diffusionpreventing film 414, the first interlayer insulating film 415, a firstCu joining portion 416 and a first Cu barrier layer 417.

The first SiO2 layer 411 is formed on the first semiconductor substrate.The first Cu wiring line portion 412 is formed in an embedded state onthe surface of the first SiO2 layer 411 on the opposite side to thefirst semiconductor substrate side. It is to be noted that the first Cuwiring line portion 412 is a Cu film extending in a predetermineddirection as seen in FIG. 15 and is connected to a predetermined device,a signal processing circuit or the like in the semiconductor device 401not shown or in an electronic apparatus including the semiconductordevice 401.

The first Cu barrier film 413 is formed between the first SiO2 layer 411and the first Cu wiring line portion 412. It is to be noted that thefirst Cu barrier film 413 is a thin film for preventing diffusion of Cu(copper) from the first Cu wiring line portion 412 into the first SiO2layer 411 and is formed, for example, from Ti, Ta, Ru or a nitride (TiN,TaN, RuN) of any of them.

The first Cu diffusion preventing film 414 is formed in a region of thefirst SiO2 layer 411 and the first Cu wiring line portion 412 other thana formation region of the first Cu barrier layer 417. It is to be notedthat the first Cu diffusion preventing film 414 is a thin film forpreventing diffusion of Cu from the first Cu wiring line portion 412into the first interlayer insulating film 415 and is configured from athin film of, for example, SiC, SiN or SiCN.

The first interlayer insulating film 415 is formed on the first Cudiffusion preventing film 414 and configured from an oxide film such asa SiO2 film.

The first Cu joining portion 416 which is a first metal film is providedin an embedded manner on the surface of the first interlayer insulatingfilm 415 on the opposite side to the first Cu diffusion preventing film414 side. It is to be noted that, in the present working example, thefirst Cu joining portion 416 is configured from a Cu film having asurface (film face) of a square shape as shown in FIG. 15. However, thepresent disclosure is not limited to this, but the surface shape of thefirst Cu joining portion 416 can be changed suitably taking variousconditions such as a required contact resistance and a design rule intoconsideration.

The first Cu barrier layer 417 is provided between the first Cu joiningportion 416 and the first Cu wiring line portion 412, first Cu diffusionpreventing film 414 and first interlayer insulating film 415 in such amanner as to cover the first Cu joining portion 416. Consequently, thefirst Cu joining portion 416 is electrically connected to the first Cuwiring line portion 412 through the first Cu barrier layer 417. It is tobe noted that the first Cu barrier layer 417 is a thin film forpreventing diffusion of Cu from the first Cu joining portion 416 intothe first interlayer insulating film 415 and is formed, for example,from Ti, Ta, Ru or a nitride of any of them.

The second semiconductor member 420 includes a second semiconductorsubstrate not shown, a second SiO2 layer 421, a second Cu wiring lineportion 422, a second Cu barrier film 423, a second Cu diffusionpreventing film 424, a second interlayer insulating film 425, a secondCu joining portion 426, a second Cu barrier layer 427 and the interfaceCu barrier film 428.

It is to be noted that the second semiconductor substrate, second SiO2layer 421 and second Cu wiring line portion 422 of the secondsemiconductor member 420 have a configuration similar to that of thefirst semiconductor substrate, first SiO2 layer 411 and first Cu wiringline portion 412 of the first semiconductor member 410. Further, thesecond Cu barrier film 423, second Cu diffusion preventing film 424 andsecond interlayer insulating film 425 of the second semiconductor member420 have a configuration similar to that of the first Cu barrier film413, first Cu diffusion preventing film 414 and first interlayerinsulating film 415 of the first semiconductor member 410.

The second Cu joining portion 426 which is a second metal film isprovided in an embedded manner on the surface of the second interlayerinsulating film 425 in the form of an insulating film on the oppositeside to the second Cu diffusion preventing film 424 side. It is to benoted that, in the present working example, the second Cu joiningportion 426 is configured form a Cu film having a surface of a squareshape as shown in FIG. 15. However, the present disclosure is notlimited to this, but the surface shape of the second Cu joining portion426 can be changed suitably taking various conditions such as a requiredcontact resistance and a design rule into consideration.

Further, in the present working example, the surface area of the secondCu joining portion 426 on the joining side, that is, on the joininginterface Sj side, or the dimension of the joining side surface, is madesmaller than that of the first Cu joining portion 416 as shown in FIGS.14 and 15. Thereupon, the size of the second Cu joining portion 426 isset such that, even if maximum joining misalignment which is estimatedbetween the first semiconductor member 410 and the second semiconductormember 420 occurs, the second Cu joining portion 426 and the firstinterlayer insulating film 415 do not contact with each other on thejoining interface Sj. More particularly, the size of the second Cujoining portion 426 is set such that, for example, if the minimumdistance between a side face of the second Cu joining portion 426 and aside face of the first Cu barrier layer 417 is represented by Δa as seenin FIG. 14, then Δa is a dimension greater than the estimated maximumjoining misalignment.

The second Cu barrier layer 427 is provided between the second Cujoining portion 426 and the second Cu wiring line portion 422, second Cudiffusion preventing film 424 and second interlayer insulating film 425in such a manner as to cover the second Cu joining portion 426.Consequently, the second Cu joining portion 426 is electricallyconnected to the second Cu wiring line portion 422 through the second Cubarrier layer 427. It is to be noted that the second Cu barrier layer427 is a thin film for preventing diffusion of Cu from the second Cujoining portion 426 into the second interlayer insulating film 425similarly to the first Cu barrier layer 417 and is formed from, forexample, Ti, Ta, Ru or any of nitrides of them.

The interface Cu barrier film 428, that is, an interface barrier film oran interface barrier section, is formed on the second interlayerinsulating film 425. In this instance, the interface Cu barrier film 428is formed such that the surface of the interface Cu barrier film 428 andthe surface of the second Cu joining portion 426 on the joining side maybe substantially in flush with each other. In other words, the interfaceCu barrier film 428 is provided in a region including a face regionwhich does not join to the second Cu joining portion 426 from within theface region of the first Cu joining portion 416 on the joining interfaceSj side. By providing the interface Cu barrier film 428 in such a regionor position as just described, diffusion of Cu from the Cu joiningportion into the interlayer insulating film in the form of a SiO2 filmthrough the opposing region of the joining interface Sj to the first Cujoining portion 416 and the second interlayer insulating film 425 can beprevented.

It is to be noted that the interface Cu barrier film 428 can be formedusing such a material as, for example, SiN, SiON, SiCN or organic resin.However, from the point of view of enhancement in close contactness witha Cu film, it is preferable to particularly form the interface Cubarrier film 428 from SiN.

[Fabrication Technique of the Semiconductor Device]

Now, a fabrication technique of the semiconductor device 401 of thepresent working example is described with reference to FIGS. 16A to 16M.It is to be noted that FIGS. 16A to 16L show schematic cross sections inthe proximity of the Cu joining portion of a semiconductor memberproduced at different steps and FIG. 16M illustrates a manner of ajoining process of the first semiconductor member 410 and the secondsemiconductor member 420.

First, a production technique of the first semiconductor member 410 isdescribed with reference to FIGS. 16A to 16F. In the present workingexample, though not shown, a first Cu barrier film 413 and a first Cuwiring line portion 412 are formed in this order in a predeterminedregion of one of the surfaces of the first SiO2 layer 411 which is aground insulating layer. Thereupon, the first Cu wiring line portion 412is formed in such a manner that it is embedded in one of the surfaces ofthe first SiO2 layer 411, that is, it is exposed to the surface of thefirst SiO2 layer 411.

Then, as shown in FIG. 16A, a first Cu diffusion preventing film 414 isformed on the surface on the first Cu wiring line portion 412 side ofthe semiconductor member configured from the first SiO2 layer 411, firstCu wiring line portion 412 and first Cu barrier film 413. It is to benoted that the first SiO2 layer 411, first Cu wiring line portion 412,first Cu barrier film 413 and first Cu diffusion preventing film 414 canbe formed by a method similar to such a fabrication method of asemiconductor device such as a solid-state image pickup device inrelated art as disclosed, for example, in Japanese Patent Laid-Open No.2004-63859.

Then, a first interlayer insulating film 415 is formed on the first Cudiffusion preventing film 414. In particular, a SiO2 film or acarbon-containing silicon oxide (SiOC) film of a thickness ofapproximately 50 to 500 nm is formed on the first Cu diffusionpreventing film 414 to form a first interlayer insulating film 415. Itis to be noted that such a first interlayer insulating film 415 as justdescribed can be formed, for example, by a CVD (Chemical VaporDeposition) method or a spin coating method.

Thereafter, a resist film 450 is formed on the first interlayerinsulating film 415 as shown in FIG. 16B. Then, a photolithographytechnique is used to carry out a patterning process for the resist film450 to remove the resist film 450 in a formation region of a first Cujoining portion 416 to form an opening 450 a.

Then, for example, a known etching apparatus of the magnetron type isused to carry out a dry etching process for the surface of thesemiconductor member, on which the resist film 450 is formed, on theopening 450 a side. Consequently, the region of the first interlayerinsulating film 415 exposed to the opening 450 a of the resist film 450is etched. By this etching process, the first interlayer insulating film415 and the first Cu diffusion preventing film 414 in the region of theopening 450 a of the resist film 450 are removed to expose the first Cuwiring line portion 412 to an opening 415 a of the first interlayerinsulating film 415 as shown in FIG. 16C. It is to be noted that, in thepresent working example, the opening diameter of the opening 415 a ofthe first interlayer insulating film 415 is, for example, approximately4 to 100 μm.

Thereafter, for example, an ashing process in which oxygen (O2) plasmais used and a washing process in which solution of organic amine-baseddrug is used are carried out for the face for which the etching processhas been carried out. By the processes, the resist film 450 remaining onthe first interlayer insulating film 415 and the residual depositsgenerated in the etching process are removed.

Then as seen in FIG. 16D, a first Cu barrier layer 417 made of Ti, Ta,Ru or any of nitrides of them is formed on the first interlayerinsulating film 415 and the first Cu wiring line portion 412 exposed tothe opening 415 a of the first interlayer insulating film 415. Inparticular, such a technique as, for example, an RF (Radio Frequency)sputtering method is used to form the first Cu barrier layer 417 of athickness of approximately 5 to 50 nm on the first interlayer insulatingfilm 415 and the first Cu wiring line portion 412 in an Ar/N2atmosphere.

Then, as shown in FIG. 16E, a Cu film 451 is formed on the first Cubarrier layer 417 using a technique such as a sputtering method or anelectrolytic plating method. By this process, the Cu film 451 isembedded in a region of the opening 415 a of the first interlayerinsulating film 415.

Thereafter, the semiconductor member on which the Cu film 451 is formedis heated to approximately 100 to 400° C. for approximately one to 60minutes in a nitrogen atmosphere or in vacuum using a heating apparatussuch as a hot plate or a sinter annealing apparatus. By this heatingprocess, the Cu film 451 is stiffened to form a Cu film 451 of fine filmquality.

Thereafter, unnecessary part of the Cu film 451 and the first Cu barrierlayer 417 is removed by a chemical mechanical polishing (CMP) method asshown in FIG. 16F. In particular, the surface of the Cu film 451 ispolished by a CMP method until the first interlayer insulating film 415is exposed to the surface.

In the present working example, the steps described hereinabove withreference to FIGS. 16A to 16F are carried out to produce a firstsemiconductor member 410. Now, a fabrication technique of the secondsemiconductor member 420 is described with reference to FIGS. 16G to16L.

First, a second Cu barrier film 423 and a second Cu wiring line portion422 are formed in this order in a predetermined region of one of facesof a second SiO2 layer 421 similarly as in fabrication of the firstsemiconductor member 410 (step of FIG. 16A). Then, a second Cu diffusionpreventing film 424 is formed on the surface of the semiconductormember, which is formed from the second SiO2 layer 421, second Cu wiringline portion 422 and second Cu barrier film 423, on the second Cu wiringline portion 422 side.

Then, a second interlayer insulating film 425 is formed on the second Cudiffusion preventing film 424. In particular, for example, on the secondCu diffusion preventing film 424, a SiO2 film or a SiOC film of athickness of approximately 50 to 500 nm is formed as a second interlayerinsulating film 425. It is to be noted that such a second interlayerinsulating film 425 as just described can be formed, for example, by aCVD method or a spin coating method. Then, on the second interlayerinsulating film 425, an interface Cu barrier film 428 of a thickness ofapproximately 5 to 100 nm is formed using a technique such as a CVDmethod or a spin coating method. Thereafter, a SiO2 film or a SiOC filmof a thickness of approximately 50 to 200 nm is formed on the interfaceCu barrier film 428 using a technique such as a CVD method or a spincoating method thereby forming an insulating film 452.

Then, a resist film 453 is formed on the insulating film 452 as shown inFIG. 16G. Then, using a photolithography technique, a patterning processis carried out for the resist film 453 to remove the resist film 153 ina formation region for the second Cu joining portion 426 to form anopening 453 a. It is to be noted that the opening diameter of theopening 453 a is set smaller than that of the opening 450 a of theresist film 450 formed at the step described hereinabove with referenceto FIG. 16B.

However, the production step of the semiconductor member wherein theopening 453 a is formed in the resist film 453 described hereinabove isnot limited to the example illustrated in FIG. 16G, and for example, theresist film 453 may be provided directly on the interface Cu barrierfilm 428 and have the opening 453 a formed therein. FIG. 16H shows aschematic cross section of the semiconductor member when the opening 453a is formed by the technique just described.

However, if the technique illustrated in FIG. 16H is adopted, then a Cufilm is directly formed on the interface Cu barrier film 428 through asecond Cu barrier layer 427, and then the Cu film is polished by a CMPprocess to form a second Cu joining portion 426. However, since usuallythe interface Cu barrier film 428 is a film difficult to polish by a CMPmethod, where the technique illustrated in FIG. 16H is adopted, upon CMPprocessing, a portion of the Cu film which remains without being removedmay appear on the interface Cu barrier film 428.

In contrast, in the formation method of the opening 453 a illustrated inFIG. 16G, since the insulating film 452 is formed on the interface Cubarrier film 428, the portion of the Cu film which remains without beingremoved can be eliminated with a higher degree of certainty by polishingalso the insulating film 452 upon CMP processing of the Cu film. Inother words, from a point of view of prevention of appearance of anunremoved portion of the Cu film when the second Cu joining portion 426is formed, the formation technique of the opening 453 a illustrated inFIG. 16G is more preferable than the formation technique of the opening453 a illustrated in FIG. 16H.

Then, a dry etching process is carried out for the surface of thesemiconductor member, on which the resist film 453 is formed, on theopening 453 a side using a known etching apparatus of the magnetrontype. Consequently, a region of the insulating film 452 exposed to theopening 453 a of the resist film 453 is etched. By this etching process,the insulating film 452, interface Cu barrier film 428, secondinterlayer insulating film 425 and second Cu diffusion preventing film424 in the region of the opening 453 a are removed as shown in FIG. 16Ito expose the second Cu wiring line portion 422 to an opening 425 a ofthe second interlayer insulating film 425. It is to be noted that theopening diameter of the opening 425 a of the second interlayerinsulating film 425 is, for example, approximately 1 to 95 μm.

Thereafter, for example, an ashing process in which oxygen (O2) plasmais used and a washing process in which solution of organic amine-baseddrug is used are carried out for the face for which the etching has beencarried out. By the processes, the resist film 453 remaining on theinsulating film 452 and the residual deposits generated in the etchingprocess are removed.

Then as seen in FIG. 16J, a second Cu barrier layer 427 made of Ti, Ta,Ru or any of nitrides of them is formed on the insulating film 452 andthe second Cu wiring line portion 422 exposed to the opening 425 a ofthe second interlayer insulating film 425. In particular, such atechnique as, for example, an RF sputtering method is used to form asecond Cu barrier layer 427 of a thickness of approximately 5 to 50 nmon the insulating film 452 and the second Cu wiring line portion 422 inan Ar/N2 atmosphere.

Then, as shown in FIG. 16K, a Cu film 454 is formed on the second Cubarrier layer 427 using a technique such as a sputtering method or anelectrolytic plating method. By this process, the Cu film 454 isembedded in a region of the opening 425 a of the second interlayerinsulating film 425.

Thereafter, the semiconductor member on which the Cu film 454 is formedis heated to approximately 100 to 400° C. for approximately one to 60minutes in a nitrogen atmosphere or in vacuum using a heating apparatussuch as a hot plate or a sinter annealing apparatus. By this heatingprocess, the Cu film 454 is stiffened to form a Cu film 454 of fine filmquality.

Thereafter, unnecessary part of the Cu film 454, second Cu barrier layer427 and the insulating film 452 is removed by a chemical mechanicalpolishing (CMP) method as shown in FIG. 16L. In particular, the surfaceon the Cu film 454 side is polished by a CMP method until the interfaceCu barrier film 428 is exposed to the surface. In the present workingexample, the various steps described hereinabove with reference to FIGS.16G to 16L are carried out to produce the second semiconductor member420.

Thereafter, the first semiconductor member 410 shown in FIG. 16F and thesecond semiconductor member 420 shown in FIG. 16L produced by theprocedures described above are bonded to each other. The particularprocessing substance of the bonding step, that is, a joining step, issuch as described below.

First, a reduction process is carried out for the surface of the firstsemiconductor member 410 on the first Cu joining portion 416 side andthe surface of the second semiconductor member 420 on the second Cujoining portion 426 side to remove an oxide film, that is, to removeoxides, on the surface of the Cu joining portions. By such removal,clean Cu is exposed to the surface of the Cu joining portions. It is tobe noted that, as the reduction process in this instance, a wet etchingprocess in which solution of drug such as formic acid is used or a dryetching process in which plasma of, for example, Ar, NH3 or H2 is usedis used.

Then, the surface of the first semiconductor member 410 on the first Cujoining portion 416 side and the surface of the second semiconductormember 420 on the second Cu joining portion 426 side are contacted witheach other or bonded to each other as shown in FIG. 16M. Thereupon, thefirst Cu joining portion 416 and the corresponding second Cu joiningportion 426 are bonded to each other after they are positioned so as tooppose to each other.

Then, in the state in which the first semiconductor member 410 and thesecond semiconductor member 420 are bonded to each other, a heatingapparatus such as a hot plate or a RTA (Rapid Thermal Annealing)apparatus is used to anneal the bonded members to join the first Cujoining portion 416 and the second Cu joining portion 426 to each other.In particular, the bonded members are heated to approximately 100 to400° C. for approximately five minutes to two hours, for example, in anN2 atmosphere of the atmospheric pressure or in vacuum.

Further, by this joining process, an interface Cu barrier film 428 isdisposed in region, from within the face region of the first Cu joiningportion 416 on the joining interface Sj side, including the face regionwhich is not joined to the second Cu joining portion 426. Moreparticularly, as shown in FIG. 14, an interface Cu barrier film 428 isdisposed in the region including the region of the joining interface Sjin which the first Cu joining portion 416 and the second interlayerinsulating film 425 are opposed to each other.

In the present working example, a Cu—Cu joining process is carried outin this manner. It is to be noted that the fabrication technique for thesemiconductor device 401 other than the joining step described above maybe similar to a fabrication technique for a semiconductor device such asa solid-state image pickup device (refer to, for example, JapanesePatent Laid-Open No. 2007-234725).

As described above, in the semiconductor device 401 of the presentworking example, the interface Cu barrier film 428 is provided in theregion including the joining interface region in which the first Cujoining portion 416 of the first semiconductor member 410 and the secondinterlayer insulating film 425 of the second semiconductor member 420are opposed to each other. Therefore, in the present working example,even if joining misalignment occurs upon joining of semiconductormembers, a contact region between the Cu joining portion and theinterlayer insulating film does not appear on the joining interface Sj,and the failure in electric characteristic on the joining interface Sjdescribed hereinabove can be eliminated.

Further, in the present working example, the surface area of the firstCu joining portion 416 on the joining side is made sufficiently greaterthan that of the second Cu joining portion 426 as described hereinabove.Therefore, in the present working example, even if misalignment occursupon joining of the first semiconductor member 410 and the secondsemiconductor member 420 to each other, the contact area and hence thecontact resistance between the Cu joining portions do not vary, anddeterioration of the electric characteristic or performance of thesemiconductor device 401 can be suppressed. In particular, since, in thepresent working example, increase of the contact resistance of thejoining interface Sj can be suppressed, increase of the powerconsumption of the semiconductor device 401 and drop of the processingspeed can be suppressed.

Further, in the present working example, since the interface Cu barrierfilm 428 is provided between the first Cu joining portion 416 and thesecond interlayer insulating film 425, the close contacting forcebetween them can be enhanced. Consequently, in the present workingexample, the joining strength between the first semiconductor member 410and the second semiconductor member 420 can be increased.

From the foregoing, according to the present working example, thesemiconductor device 401 can be provided wherein degradation of anelectric characteristic on the joining interface can be suppressedfurther and which has a joining interface Sj of a higher degree ofreliability.

2. Second Working Example Configuration of the Semiconductor Device

FIGS. 17 and 18 show a general configuration of a semiconductor deviceaccording to a second working example of the third embodiment. Inparticular, FIG. 17 shows a schematic cross section of the semiconductordevice according to the second working example in the proximity of ajoining interface, and FIG. 18 shows a schematic top plan in theproximity of the joining interface and illustrates an arrangementrelationship of Cu joining portions and an interface Cu barrier film. Itis to be noted that, in FIGS. 17 and 18, only a configuration in theproximity of a joining interface is shown for simplified description.Further, in the semiconductor device 402 of the present working exampleshown in FIGS. 17 and 18, like elements to those of the semiconductordevice 401 of the first working example shown in FIGS. 14 and 15 aredenoted by like reference characters.

Referring first to FIG. 17, the semiconductor device 402 includes afirst semiconductor member 430 which is a first semiconductor section, asecond semiconductor member 440 which is a second semiconductor section,and an interface Cu barrier film 450 which is an interface barrier filmor interface barrier section.

The first semiconductor member 430 includes a first semiconductorsubstrate not shown, a first SiO2 layer 411, a first Cu wiring lineportion 412, a first Cu barrier film 413, a first Cu diffusionpreventing film 414, a first interlayer insulating film 415, a first Cujoining portion 416, a first Cu barrier layer 417 and a first Cu seedlayer 431.

As can be recognized from comparison between FIGS. 17 and 14, the firstsemiconductor member 430 in the present working example is configuredsuch that the first Cu seed layer 431 is provided between the first Cujoining portion 416 and the first Cu barrier layer 417 in the firstsemiconductor member 410 of the first working example. The configurationof the other part of the first semiconductor member 430 is similar tothat of the first semiconductor member 410 of the first working exampledescribed hereinabove. Therefore, description is given below only of theconfiguration of the first Cu seed layer 431.

The first Cu seed layer 431 which is a seed layer is provided betweenthe first Cu joining portion 416 and the first Cu barrier layer 417 asdescribed above and is provided so as to cover the first Cu joiningportion 416.

The first Cu seed layer 431 is formed from a Cu layer or a Cu alloylayer containing a metal material which is likely to react with oxygen.As the metal material contained in the first Cu seed layer 431, forexample, a metal material which is more likely to react with oxygen thanhydrogen can be used. In particular, metal materials of Fe, Mn, V, Cr,Mg, Si, Ce, Ti, Al and so forth can be used. It is to be noted that,among the metal materials mentioned, Mn, Mg, Ti or Al is a materialsuitable for the semiconductor device. Further, from a point of view ofreduction of the wiring line resistance of the joining interface Sj, itis particularly preferable to use Mn or Ti as the metal material to becontained in the first Cu seed layer 431.

The second semiconductor member 440 includes a second semiconductorsubstrate not shown, a second SiO2 layer 421, a second Cu wiring lineportion 422, a second Cu barrier film 423, a second Cu diffusionpreventing film 424, a second interlayer insulating film 425, a secondCu joining portion 426, a second Cu barrier layer 427 and a second Cuseed layer 441.

As apparently recognized from FIGS. 17 and 14, the second semiconductormember 440 in the present working example is configured such that thesecond semiconductor member 420 of the first working example does notinclude the interface Cu barrier film 428 but includes the second Cuseed layer 441 provided between the second Cu joining portion 426 andthe second Cu barrier layer 427. The configuration of the other part ofthe second semiconductor member 440 is similar to that of the secondsemiconductor member 420 of the first working example describedhereinabove. Therefore, the configuration only of the second Cu seedlayer 441 is described below.

The second Cu seed layer 441 is provided between the second Cu joiningportion 426 and the second Cu barrier layer 427 as described hereinaboveand is formed so as to cover the second Cu joining portion 426. Thesecond Cu seed layer 441 is formed from a Cu layer or a CU alloy layercontaining a metal material which is likely to react with oxygensimilarly to the first Cu seed layer 431. Further, the metal materialcontained in the second Cu seed layer 441 can be suitably selected fromamong the metal materials described in regard to the first Cu seed layer431. It is to be noted that, in the present working example, the metalmaterial contained in the second Cu seed layer 441 is same as thatcontained in the first Cu seed layer 431.

The interface Cu barrier film 450 is a film produced by heat treatment,that is, by an annealing process, when the first semiconductor member430 and the second semiconductor member 440 are joined together, byreaction of metal materials contained in the Cu seed layers and oxygenin the pertaining interlayer insulating films, principally in the secondinterlayer insulating film 425. In other words, the interface Cu barrierfilm 450 is a self-forming film. Therefore, the interface Cu barrierfilm 450 is formed in a region of the joining interface Sj across whichthe first Cu joining portion 416 of the first semiconductor member 430and the second interlayer insulating film 425 of the secondsemiconductor member 440 oppose to each other, and is configured from anoxide film of, for example, MnOx, MgOx, TiOx or AlOx.

It is to be noted that, in FIG. 17, in order to clearly indicate theformation position of the interface Cu barrier film 450, it is shownthat the interface Cu barrier film 450 is formed so as to extend from aside face of the second Cu joining portion 426 to a side face of thefirst Cu barrier layer 417 along the joining interface Sj. However, theformation region of the interface Cu barrier film 450 is not limited tothis.

The interface Cu barrier film 450 is a film for preventing diffusion ofCu from a Cu joining portion into an interlayer insulating film throughthe opposing region between the first Cu joining portion 416 and thesecond interlayer insulating film 425. Therefore, the interface Cubarrier film 450 may be formed at least in the opposing region betweenthe first Cu joining portion 416 and the second interlayer insulatingfilm 425 along the joining interface Sj. It is to be noted that theformation region of the interface Cu barrier film 450 can be setsuitably, for example, by adjusting annealing conditions upon a joiningprocess between the first semiconductor member 430 and the secondsemiconductor member 440, the content of a metal material in each Cuseed layer and so forth.

[Fabrication Technique of the Semiconductor Device]

Now, a fabrication technique of the semiconductor device 402 of thepresent working example is described with reference to FIGS. 19A to 19E.It is to be noted that FIGS. 19A to 19D show schematic cross sections inthe proximity of a Cu joining portion of semiconductor members producedat the individual steps, and FIG. 19E illustrates a manner of a joiningprocess between the first semiconductor member 430 and the secondsemiconductor member 440. It is to be noted that, in the followingdescription, description of steps similar to those of the fabricationtechnique for a semiconductor device according to the first workingexample is given suitably referring to the figures illustrating thesteps in the first working example, that is, FIGS. 16A to 16M.

First, in the present working example, a first Cu barrier film 413, afirst Cu wiring line portion 412 and a first Cu diffusion preventingfilm 414 are formed in this order on a first SiO2 layer 411 similarly asin the fabrication process of the first semiconductor member 410 in thefirst working example described hereinabove with reference to FIG. 16A.Then, a first interlayer insulating film 415 which is a first oxide filmand an opening 415 a of the first interlayer insulating film 415 areformed on the first Cu diffusion preventing film 414 similarly as in thefabrication process of the first semiconductor member 410 in the firstworking example described hereinabove with reference to FIGS. 16B and16C. It is to be noted that, also in the present working example, theopening diameter of the opening 415 a of the first interlayer insulatingfilm 415 is, for example, approximately 4 to 100 μm. Further, a first Cubarrier layer 417 is formed on the first interlayer insulating film 415and the first Cu wiring line portion 412 exposed to the opening 415 a ofthe first interlayer insulating film 415 similarly as in the fabricationprocess of the first semiconductor member 410 in the first workingexample described hereinabove with reference to FIG. 16D.

Then, as shown in FIG. 19A, a first Cu seed layer 431 of a thickness ofapproximately 5 to 50 nm is formed on the first Cu barrier layer 417 inan Ar/N2 atmosphere using a technique of, for example, an RF sputteringmethod. The first Cu seed layer 431 may be, for example, a CuMn layer, aCuAl layer, a CuMg layer or a CuTi layer.

Then, as shown in FIG. 19B, a Cu film 455 is formed on the first Cu seedlayer 431 using a technique such as a sputtering method or anelectrolytic plating method. By this process, the Cu film 455 isembedded in the region of the opening 415 a of the first interlayerinsulating film 415.

Thereafter, the semiconductor member on which the Cu film 455 is formedis heated at approximately 100 to 400° C. for approximately one to 60minutes in a nitrogen atmosphere or in vacuum using a heating apparatussuch as a hot plate or a sinter annealing apparatus. By this heatingprocess, the Cu film 455 is stiffened to form a Cu film 455 of fine filmquality.

Then, as shown in FIG. 19C, unnecessary part of the Cu film 455, firstCu seed layer 431 and first Cu barrier layer 417 is removed by a CMPmethod. In particular, the surface of the Cu film 455 side is polishedby a CMP method until the first interlayer insulating film 415 isexposed to the surface.

In the present working example, the first semiconductor member 430 isproduced in such a manner as described above. Further, in the presentworking example, the second semiconductor member 440 is producedsimilarly to the first semiconductor member 430 described above.

FIG. 19D shows a schematic cross section of the second semiconductormember 440 produced in accordance with the present working example.However, in the present working example, when an opening is formed inthe second interlayer insulating film 425 which is a second oxide filmhalfway of production of the second semiconductor member 440, theopening diameter of the opening is made smaller than the openingdiameter in the first interlayer insulating film 415 describedhereinabove with reference to FIG. 16C, that is, smaller thanapproximately 4 to 100 μm. More particularly, the opening diameter ofthe opening in the second interlayer insulating film 425 is set toapproximately 1 to 95 μm.

Thereafter, the first semiconductor member 430 shown in FIG. 19C and thesecond semiconductor member 440 shown in FIG. 19D, both produced in sucha manner as described above, are bonded to each other similarly as inthe first working example.

In particular, a reduction process is carried out for the surface of thefirst semiconductor member 430 on the first Cu joining portion 416 sideand the surface of the second semiconductor member 440 on the second Cujoining portion 426 side to remove an oxide film or oxides on thesurface of each Cu joining portion to expose clean Cu to the surface ofeach Cu joining portion. It is to be noted that, as the reductionprocess in this instance, a wet etching process in which solution ofdrug such as formic acid is used or a dry etching process in whichplasma of, for example, Ar, NH3 or H2 is used is used.

Then, the surface of the first semiconductor member 430 on the first Cujoining portion 416 side and the surface of the second semiconductormember 440 on the second Cu joining portion 426 side are contacted withor bonded to each other as seen in FIG. 19E. Then, in the state in whichthe first semiconductor member 430 and the second semiconductor member440 are bonded to each other, the bonded member is annealed using aheating apparatus such as a hot plate or a RTA apparatus to join thefirst Cu joining portion 416 and the second Cu joining portion 426 toeach other. In particular, the bonded member is heated, for example, atapproximately 100 to 400° C. for approximately five minutes to two hoursin an N2 atmosphere of the atmospheric pressure or in vacuum.

Further, upon the joining process described above, metal materials inthe Cu seed layers such as Mn, Mg, Ti or Al selectively react withoxygen in the interlayer insulating films, principally in the secondinterlayer insulating film 425. Consequently, an interface Cu barrierfilm 450 is formed in a region of the joining interface Sj in which thefirst Cu joining portion 416 of the first semiconductor member 430 andthe second interlayer insulating film 425 of the second semiconductormember 440 oppose to each other. In particular, by the joining processdescribed above, the interface Cu barrier film 450 is provided in aregion including, from within the face region of the first Cu joiningportion 416 on the joining interface Sj side, the face region in whichthe first Cu joining portion 416 is not joined to the second Cu joiningportion 426.

In the present working example, a Cu—Cu joining process is carried outin such a manner as described above. It is to be noted that thefabrication process of the semiconductor device 402 except the joiningstep described above may be similar to that in an existing fabricationtechnique of a semiconductor device such as a solid-state image pickupdevice, and for example, similar to the fabrication technique disclosedin Japanese Patent Laid-Open No. 2007-234725.

As described above, also in the semiconductor device 402 of the presentworking example, the interface Cu barrier film 450 is provided in theregion of the joining interface Sj in which the first Cu joining portion416 of the first semiconductor member 430 and the second interlayerinsulating film 425 of the second semiconductor member 440 oppose toeach other similarly as in the first working example describedhereinabove. Therefore, also in the present working example, effectssimilar to those achieved by the first working example are achieved.

Further, in the case where a Cu seed layer is provided and a Cu joiningsection is formed on the Cu seed layer by an electrolytic plating methodas in the present working example, Cu in the Cu seed layer serves as acore of a Cu plating film. Therefore, in the present working example,the close contacting force between the Cu joining portion and theassociated interlayer insulating film can be enhanced.

3. Third Working Example Configuration of the Semiconductor Device

FIGS. 20 and 21 show a general configuration of a semiconductor deviceaccording to a third working example of the third embodiment of thedisclosed technology. In particular, FIG. 20 shows a schematic crosssection in the proximity of a joining interference of the semiconductordevice according to the present working example, and FIG. 21 shows aschematic top plan in the proximity of the joining interface andillustrates an arrangement relationship between Cu joining portions andan interface layer portion of a second Cu barrier layer hereinafterdescribed. It is to be noted that, in FIGS. 20 and 21, in order tosimplify description, a configuration of only one joining interface isshown. Further, in the semiconductor device 403 of the present workingexample shown in FIGS. 20 and 21, like elements to those in thesemiconductor device 401 of the first working example describedhereinabove with reference to FIGS. 14 and 15 are denoted by likereference characters.

Referring first to FIG. 20, the semiconductor device 403 includes afirst semiconductor member 410 which is a first semiconductor section,and a second semiconductor member 460 which is a second semiconductorsection. It is to be noted that the first semiconductor member 410 inthe semiconductor device 403 of the present working example has aconfiguration similar to that in the semiconductor device 401 of thefirst working example described hereinabove with reference to FIG. 14.Therefore, overlapping description of the first semiconductor member 410is omitted herein to avoid redundancy.

The second semiconductor member 460 includes a second semiconductorsubstrate not shown, a second SiO2 layer 421, a second Cu wiring lineportion 422, a second Cu barrier film 423, a second Cu diffusionpreventing film 424, a second interlayer insulating film 425, a secondCu joining portion 426 and a second Cu barrier layer 461 which is abarrier metal layer.

As apparent from comparison between FIGS. 20 and 14, the secondsemiconductor member 460 in the present working example is configuredsuch that the second semiconductor member 420 in the first workingexample does not include the interface Cu barrier layer 428 but ischanged in configuration of the second Cu barrier layer 427. Theconfiguration of the other part of the second semiconductor member 460is similar to that of the corresponding part of the second semiconductormember 420 of the first working example described hereinabove.Therefore, only the configuration of the second Cu barrier layer 461 isdescribed below.

Referring to FIG. 20, the second Cu barrier layer 461 includes a barrierbody portion 461 a provided so as to cover the second Cu joining portion426, and an interface layer portion 461 b, which is an interface barrierportion, formed so as to extend along a joining interface Sj from an endportion of the barrier body portion 461 a on the joining interface Sjside.

In particular, in the present working example, the interface layerportion 461 b of the second Cu barrier layer 461 is disposed in a regionof the joining interface Sj in which the first Cu joining portion 416 ofthe first semiconductor member 410 and the second interlayer insulatingfilm 425 of the second semiconductor member 460 oppose to each other.Further, the interface layer portion 461 b of the second Cu barrierlayer 461 prevents Cu from diffusing from the Cu joining portion intothe interlayer insulating film through the opposing region of the firstCu joining portion 416 and the second interlayer insulating film 425.Therefore, in the present working example, the width of the interfacelayer portion 461 b in a direction along the joining interface Sj is setsuch that, even if estimated maximum misalignment occurs upon joining, acontact region between the first Cu joining portion 416 and the secondinterlayer insulating film 425 may not appear on the joining interfaceSj. It is to be noted that the second Cu barrier layer 461 is configuredfrom, for example, Ti, Ta, Ru or a nitride of them similarly as in thefirst working example described hereinabove.

[Fabrication Technique of the Semiconductor Device]

Now, a fabrication technique of the semiconductor device 403 of thepresent working example is described with reference to FIGS. 22A to 22H.It is to be noted that FIGS. 22A to 22G show schematic cross sections inthe proximity of a Cu joining portion of semiconductor members producedat individual steps, and FIG. 22H illustrates a manner of a joiningprocess of a first semiconductor member 410 and a second semiconductormember 460. Further, in description of steps similar to those of thefabrication technique of the semiconductor device of the first workingexample described hereinabove, the figures at the steps in the firstworking example, that is, FIGS. 16A to 16M, are referred to suitably.Further, since the production technique of the first semiconductormember 410 in the present working example is similar to that in thefirst working example described hereinabove with reference to FIGS. 16Ato 16F, description of the production technique of the firstsemiconductor member 410 is omitted here to avoid redundancy. Thus, aproduction technique of the second semiconductor member 460 and a Cu—Cujoining technique are described below.

First, in the present working example, a second Cu barrier film 423, asecond Cu wiring line portion 422 and a second Cu diffusion preventingfilm 424 are formed in this order on a second SiO2 layer 421 in asimilar manner as in the production step of the first semiconductormember 410 of the first working example described hereinabove withreference to FIG. 16A. Then, a second interlayer insulating film 425 isformed on the second Cu diffusion preventing film 424 in a similarmanner as in the production step of the first semiconductor member 410in the first working example described hereinabove with reference toFIG. 16B.

Then, a resist film 456 is formed on the second interlayer insulatingfilm 425 as shown in FIG. 22A. Then, a patterning process is carried outfor the resist film 456 using a photolithography technique to remove theresist film 456 in a formation region for a second Cu barrier layer 461to form an opening 456 a. Consequently, the second interlayer insulatingfilm 425 is exposed to the opening 456 a of the resist film 456.

Then, a dry etching process is carried out for the surface of thesemiconductor member, on which the resist film 456 is formed, on theopening 456 a side using a known etching apparatus of the magnetrontype. Consequently, the region of the second interlayer insulating film425 exposed to the opening 456 a of the resist film 456 is etched.Thereupon, the second interlayer insulating film 425 is removed byapproximately 10 to 50 nm by the etching. As a result, a recessedportion 425 b of a depth of approximately 10 to 50 nm is formed on thesurface of the second interlayer insulating film 425 as shown in FIG.22B.

Thereafter, for example, an ashing process in which oxygen (O2) plasmais used and a washing process in which solution of organic amine-baseddrug is used are carried out for the face for which the etching has beencarried out. By the processes, the resist film 456 remaining on thesecond interlayer insulating film 425 and the residual depositsgenerated in the etching process are removed.

Then, a resist film 457 is formed on the second interlayer insulatingfilm 425 as shown in FIG. 22C. Then, a patterning process is carried outfor the resist film 457 using a photolithography technique to remove theresist film 457 in a formation region for a barrier body portion 461 aof a second Cu barrier layer 461 to form an opening 457 a. Consequently,the bottom of the recessed portion 425 b of the second interlayerinsulating film 425 is exposed to the opening 457 a of the resist film457.

Thereafter, a dry etching process is carried out for the surface of thesemiconductor member, on which the resist film 457 is formed, on theopening 457 a side using, for example, a known etching apparatus of themagnetron type. Consequently, the region of the recessed portion 425 bof the second interlayer insulating film 425 exposed to the opening 457a of the resist film 457 is partly etched.

In this etching process, the second interlayer insulating film 425 andthe second Cu diffusion preventing film 424 in the region of the opening457 a are removed to expose the second Cu wiring line portion 422 to anopening 425 a of the second interlayer insulating film 425 as shown inFIG. 22D. Further, in the present working example, the opening diameterof the opening 425 a of the second interlayer insulating film 425 isset, for example, to approximately 1 to 95 μm. It is to be noted thatthe region of the recessed portion 425 b of the second interlayerinsulating film 425 from which the second interlayer insulating film 425is not removed in this etching process is a formation region for theinterface layer portion 461 b of the second Cu barrier layer 461.

Thereafter, for example, an ashing process in which oxygen (O2) plasmais used and a washing process in which solution of organic amine-baseddrug is used are carried out for the face for which the etching processhas been carried out. By the processes, the resist film 457 remaining onthe second interlayer insulating film 425 and the residual depositsgenerated in the etching process are removed.

Then as seen in FIG. 22E, a second Cu barrier layer 461 made of Ti, Ta,Ru or any of nitrides of them is formed on the second interlayerinsulating film 425 and the second Cu wiring line portion 422 exposed tothe opening 425 a of the second interlayer insulating film 425. Inparticular, such a technique as, for example, an RF sputtering method isused to form a second Cu barrier layer 461 of a thickness ofapproximately 5 to 50 nm on the second interlayer insulating film 425and the second Cu wiring line portion 422 in an Ar/N2 atmosphere. Bythis process, a barrier body portion 461 a is formed on the second Cuwiring line portion 422 exposed to the opening 425 a of the secondinterlayer insulating film 425 and on a side face of the secondinterlayer insulating film 425. Further, by the process described above,an interface layer portion 461 b is formed on the recessed portion 425 bof the second interlayer insulating film 425.

Thereafter, a Cu film 458 is formed on the second Cu barrier layer 461as shown in FIG. 22F using, for example, a technique of a sputteringmethod or an electrolytic plating method. By this process, the Cu film458 is embedded in the region of the opening 425 a of the secondinterlayer insulating film 425.

Then, the semiconductor member on which the Cu film 458 is formed isheated at approximately 100 to 400° C. for approximately one to 60minutes in a nitrogen atmosphere or in vacuum using a heating apparatussuch as a hot plate or a sinter annealing apparatus. By the heatingprocess, the Cu film 458 is stiffened to form a Cu film 458 of fine filmquality.

Then, unnecessary part of the Cu film 458 and the second Cu barrierlayer 461 are removed by a chemical mechanical polishing (CMP) method asshown in FIG. 22G. Thereupon, processing conditions of the CMP methodare adjusted such that the interface layer portion 461 b may remain onthe recessed portion 425 b of the second interlayer insulating film 425.In particular, the surface of the Cu film 458 is polished by a CMPmethod until the second interlayer insulating film 425 is exposed to thesurface. In the present working example, a second semiconductor member460 is produced in such a manner as described above.

Thereafter, the second semiconductor member 460 shown in FIG. 22Gproduced in such a manner as described above and the first semiconductormember 410 shown in FIG. 16F produced in a similar manner as in thefirst working example described hereinabove are bonded to each other ina similar manner as in the first working example.

In particular, a reduction process is carried out for the surface of thefirst semiconductor member 410 on the first Cu joining portion 416 sideand the surface of the second semiconductor member 460 on the second Cujoining portion 426 side to remove an oxide film or oxides on thesurface of each Cu joining portion to expose clean Cu to the surface ofeach Cu joining portion. It is to be noted that, as the reductionprocess in this instance, a wet etching process in which solution ofdrug such as formic acid is used or a dry etching process in whichplasma of, for example, Ar, NH3 or H2 is used is used.

Then, the surface of the first semiconductor member 410 on the first Cujoining portion 416 side and the surface of the second semiconductormember 460 on the second Cu joining portion 426 side are contacted withor bonded to each other as seen in FIG. 22H. Then, in the state in whichthe first semiconductor member 410 and the second semiconductor member460 are bonded to each other, the bonded member is annealed using aheating apparatus such as a hot plate or a RTA apparatus to join thefirst Cu joining portion 416 and the second Cu joining portion 426 toeach other. In particular, the bonded member is heated, for example, atapproximately 100 to 400° C. for approximately five minutes to two hoursin an N2 atmosphere of the atmospheric pressure or in vacuum.

Further, by the joining process described above, an interface layerportion 461 b of the second Cu barrier layer 461 is disposed in a regionwhich includes, from within a face region of the first Cu joiningportion 416 on the joining interface Sj side, a face region which is notjoined to the second Cu joining portion 426. More particularly, theinterface layer portion 461 b of the second Cu barrier layer 461 isdisposed in the region including the region of the joining interface Sjin which the first Cu joining portion 416 and the second interlayerinsulating film 425 are opposed to each other as shown in FIG. 20.

In the present working example, a Cu—Cu joining process is carried outin such a manner as described above. It is to be noted that thefabrication process of the semiconductor device 402 except the joiningstep described above may be similar to that in an existing fabricationtechnique of a semiconductor device such as a solid-state image pickupdevice, and for example, similar to the fabrication technique disclosedin Japanese Patent Laid-Open No. 2007-234725.

As described above, also in the present working example, the interfacelayer portion 461 b of the second Cu barrier layer 461 is provided inthe region of the joining interface Sj in which the first Cu joiningportion 416 of the first semiconductor member 410 and the secondinterlayer insulating film 425 of the second semiconductor member 460oppose to each other similarly as in the first working example describedhereinabove. Therefore, also in the present working example, effectssimilar to those achieved by the first working example are achieved.

4. Various Modifications and Reference Examples

Now, various modifications to the semiconductor devices of the workingexamples described hereinabove are described.

[Modification 1]

While, in the semiconductor device 401 of the first working exampledescribed hereinabove with reference to FIG. 14, the second Cu diffusionpreventing film 424, second interlayer insulating film 425 and interfaceCu barrier layer 428 are provided on the second Cu wiring line portion422 of the second semiconductor member 420, the present disclosure isnot limited to this configuration. For example, another configurationwherein an interface Cu barrier film is provided only on the second Cuwiring line portion 422 may be used.

An example of the configuration, that is, a modification 1, is shown inFIG. 23. FIG. 23 particularly shows a schematic cross section of asemiconductor device 404 of the modification 1 in the proximity of thejoining interface Sj. It is to be noted that, in the semiconductordevice 404 of the modification 1, like elements to those in thesemiconductor device 401 of the first working example describedhereinabove with reference to FIG. 14 are denoted by like referencecharacters.

Referring to FIG. 23, the semiconductor device 404 includes a firstsemiconductor member 410 and a second semiconductor member 470. It is tobe noted that, since the first semiconductor member 410 of thesemiconductor device 404 of the present modification 1 has aconfiguration similar to that of the first working example describedhereinabove with reference to FIG. 14, description of the firstsemiconductor member 410 is omitted herein to avoid redundancy.

The second semiconductor member 470 includes a second semiconductorsubstrate not shown, a second SiO2 layer 421, a second Cu wiring lineportion 422, a second Cu barrier film 423, an interface Cu barrier film471 which is an interface barrier film or interface barrier section, asecond Cu joining portion 426, and a second Cu barrier layer 427. It isto be noted that the other part than the interference Cu barrier film471 of the second semiconductor member 470 is similar in configurationto the corresponding part of the second semiconductor member 420 in thefirst working example described hereinabove.

The interface Cu barrier film 471 which is a Cu diffusion preventingfilm is provided on the second SiO2 layer 421, second Cu wiring lineportion 422 and second Cu barrier film 423 and besides is provided insuch a manner as to cover a side portion of the second Cu barrier layer427. Therefore, in the present example, the interface Cu barrier film471 not only prevents diffusion of Cu from the Cu joining portion intothe interlayer insulating film but also plays roles similar to those ofthe second Cu diffusion preventing film 424 and the second interlayerinsulating film 425 of the second semiconductor member 420 of the firstworking example described hereinabove.

It is to be noted that the interface Cu barrier film 471 may be formedfrom a material such as SiN, SiON, SiCN or an organic resin similarly tothe interface Cu barrier film 428 in the first working example.

The second semiconductor member 470 in the present modification can beproduced, for example, in the following manner. First, a second Cubarrier film 423 and a second Cu wiring line portion 422 are formed inthis order on a second SiO2 layer 421 in a similar manner as at theproduction step of the first semiconductor member 410 of the firstworking example described hereinabove with reference to FIG. 16A. Then,an interface Cu barrier film 471 of a thickness of approximately 5 to500 nm is formed on the second SiO2 layer 421, second Cu wiring lineportion 422 and second Cu barrier film 423.

Then, a resist film 459 is formed on the interface Cu barrier film 471as shown in FIG. 24. Thereafter, a photolithography technique is used tocarry out a patterning process for the resist film 459 to remove theresist film 459 in a formation region for the second Cu joining portion426 to form an opening 459 a. Consequently, the interface Cu barrierfilm 471 is exposed to the opening 459 a of the resist film 459.Thereafter, the production steps for the second semiconductor member 420in the first working example described hereinabove with reference toFIGS. 16I to 16L are carried out to produce a second semiconductormember 470 of the present modification.

In the configuration of the present modification, a portion of the faceregion of the first Cu joining portion 416 on the joining interface Sjside in which the first Cu joining portion 416 is not joined to thesecond Cu joining portion 426 is placed in a state in which it contactswith the interface Cu barrier film 471. Therefore, also in theconfiguration of the present modification, Cu of the Cu joining portionsdoes not diffuse into an external oxide film, and therefore, similareffects to those achieved by the first working example can be achieved.

[Modification 2]

While the second working example is an example wherein a Cu seed layeris provided in both of the first semiconductor member 430 and the secondsemiconductor member 440 as described hereinabove with reference to FIG.17, the present disclosure is not limited to this. The Cu seed layer maybe provided at least in that one of the semiconductor members which hasa greater surface area on the joining side of the Cu joining portion.For example, in the semiconductor device 402 shown in FIG. 17, a Cu seedlayer may be provided only between the first Cu joining portion 416 andthe first Cu barrier layer 417 of the first semiconductor member 430.

Also in this case, by the annealing process upon joining, a metalmaterial such as Mn, Mg, Ti or Al in the Cu seed layer of the firstsemiconductor member 430 reacts with oxygen in the second interlayerinsulating film 425 of the second semiconductor member 440 which opposesto the Cu seed layer across the joining interface Sj. As a result, alsoin the present modification, an interface barrier film is formed in theregion of the joining interface Sj across which the first Cu joiningportion 416 of the first semiconductor member 430 and the secondinterlayer insulating film 425 of the second semiconductor member 440oppose to each other, and similar effects to those achieved by the firstworking example are achieved.

[Modification 3]

While the third working example described hereinabove is configured suchthat the interface layer portion 461 b of the second Cu barrier layer461 in the second semiconductor member 460 is formed in such a manner asto be embedded in the joining side surface of the second interlayerinsulating film 425, the present disclosure is not limited to this. Forexample, the second Cu barrier layer 461 may be configured otherwisesuch that the interface layer portion 461 b is provided on the joiningside surface of the second interlayer insulating film 425.

An example of the configuration, that is, a modification 3, is shown inFIG. 25. Particularly, FIG. 25 shows a schematic cross section of asemiconductor device 405 of the modification 3 in the proximity of thejoining interface Sj. It is to be noted that, in the semiconductordevice 405 of the modification 3 shown in FIG. 25, like elements tothose in the semiconductor device 403 of the third working exampledescribed hereinabove with reference to FIG. 20 are denoted by likereference characters.

Referring to FIG. 25, the semiconductor device 405 of the presentmodification includes a first semiconductor member 410 and a secondsemiconductor member 480. It is to be noted that, since theconfiguration of the first semiconductor member 410 in the semiconductordevice 405 of the present modification is similar to that in the thirdworking example described hereinabove with reference to FIG. 20,overlapping description of the first semiconductor member 410 is omittedherein to avoid redundancy.

The second semiconductor member 480 includes a second semiconductorsubstrate not shown, a second SiO2 layer 421, a second Cu wiring lineportion 422, a second Cu barrier film 423, a second Cu diffusionpreventing film 424, a second interlayer insulating film 481, a secondCu joining portion 426, a second Cu barrier layer 461 and an interfaceCu barrier film 482.

It is to be noted that, in the second semiconductor member 480 of thepresent modification, the second semiconductor substrate not shown,second SiO2 layer 421, second Cu wiring line portion 422, second Cubarrier film 423 and second Cu diffusion preventing film 424 areconfigured similarly to the corresponding components of the secondsemiconductor member 460 of the third working example describedhereinabove. Further, the second Cu joining portion 426 and the secondCu barrier layer 461 in the present modification are configuredsimilarly to the corresponding components of the second semiconductormember 460 of the third working example described hereinabove.

In the present modification, the interface layer portion 461 b of thesecond Cu barrier layer 461 is provided on the joining side surface ofthe second interlayer insulating film 481. Therefore, the secondrecessed portion 425 b provided in the third working example is notformed on the surface of the second interlayer insulating film 481.

Further, in the present modification, the interface Cu barrier film 482is formed on the surface of the second interlayer insulating film 481 insuch a manner as to cover a side portion or side face of the interfacelayer portion 461 b of the second Cu barrier layer 461. Further,thereupon, the film thickness of the interface Cu barrier film 482 andthe film thickness of the interface layer portion 461 b are madesubstantially equal to each other so that the surface of the interfaceCu barrier film 482 on the joining interface Sj side and the surface ofthe interface layer portion 461 b on the joining interface Sj side maybe substantially in flush with each other. It is to be noted that theinterface Cu barrier film 482 can be formed from such a material as, forexample, SiN, SiON, SiCN or an organic resin similarly to the interfaceCu barrier film 428 in the first working example.

In the present modification, in a region of the joining interface Sjother than the joining region between the first Cu joining portion 416and the second Cu joining portion 426, the first Cu joining portion 416is placed in a state in which it contacts with the interface layerportion 461 b of the second Cu barrier layer 461 and/or the interface Cubarrier film 482. Therefore, also in the configuration of the presentmodification, diffusion of Cu in the Cu joining portions into theinterlayer insulating film can be prevented, and therefore, similareffects to those achieved by the first working example are achieved.

It is to be noted that the present modification may be further modifiedsuch that it does not include the interface Cu barrier film 482. In thisinstance, while an air gap is formed around a side portion of theinterface layer portion 461 b of the second Cu barrier layer 461, sincediffusion of Cu of the Cu joining portions into the interlayerinsulating film can be prevented by the air cap, similar effects tothose achieved by the first working example can be achieved. However,from a point of view of the joining strength at the joining interfaceSj, it is preferable to provide the interface Cu barrier film 482 insuch a manner as to cover a side portion of the interface layer portion461 b as shown in FIG. 25.

[Modification 4]

While, in the working examples and the modifications described above,the electrode film of each joining portion is configured from a Cu film,the present disclosure is not limited to this. The joining portion mayotherwise be configured from a metal film formed from, for example, Al,W, Ti, TiN, Ta, TaN or Ru or a laminated film of such metal films.

For example, in the first working example, Al (aluminum) can be used asthe electrode material for the joining portions. In this instance, theinterface Cu barrier layer 428 can be configured from such a materialas, for example, SiN, SiON, SiCN or a resin similarly as in the firstworking example described hereinabove. Further, in this instance, themetal barrier layer which covers the Al joining portion is preferablyconfigured from a multilayer film formed by laminating a Ti film and aTiN film in this order from the Al joining portion side, that is, from aTi/TiN laminated film.

Further, for example, also in the configuration of the second workingexample described above, Al can be used as the electrode material forthe joining portions. However, in this instance, since Al is a materialliable to react with oxygen, there is no necessity to provide a seedlayer, that is, a Cu seed layer, for producing an interface barrierfilm.

FIG. 26 shows a schematic cross section in the proximity of the joininginterface Sj of a semiconductor device in the case where each joiningportion is formed from Al in the configuration of the second workingexample described above. It is to be noted that, in FIG. 26, in order tosimplify description, a configuration only in the proximity of an Aljoining portion while the configuration of the wiring line section isomitted. Further, in the semiconductor device 406 shown in FIG. 26, likeelements to those of the semiconductor device 402 of the second workingexample shown in FIG. 17 are denoted by like reference characters.

Referring to FIG. 26, the semiconductor device 406 of the presentmodification includes a first semiconductor member 491, a secondsemiconductor member 492 and an interface barrier film 497. The firstsemiconductor member 491 includes a first interlayer insulating film415, a first Al joining portion 493 formed in such a manner as to beembedded in the joining side surface of the first interlayer insulatingfilm 415, and a first barrier metal layer 494 provided between the firstinterlayer insulating film 415 and the first Al joining portion 493.Meanwhile, the second semiconductor member 492 includes a secondinterlayer insulating film 425, a second Al joining portion 495 formedin such a manner as to be embedded in the joining side surface of thesecond interlayer insulating film 425, and a second barrier metal layer496 provided between the second interlayer insulating film 425 and thesecond Al joining portion 495.

Also in the modification shown in FIG. 26, by an annealing processcarried out upon joining of the first semiconductor member 491 and thesecond semiconductor member 492, part of Al in the first Al joiningportion 493 reacts with oxygen in the second interlayer insulating film425 of the second semiconductor member 492 which opposes to the first Aljoining portion 493 across the joining interface Sj. As a result, theinterface barrier film 497 is formed in the region of the joininginterface Sj in which the first Al joining portion 493 and the secondinterlayer insulating film 425 oppose to each other. Therefore, also inthe present configuration example, the joining strength between thefirst semiconductor member 491 and the second semiconductor member 492can be increased similarly as in the first working example, and theresulting semiconductor device 406 has a joining interface of a higherdegree of reliability.

Further, for example, in the first working example, for example, W(tungsten) can be used as the electrode material for the joiningportions. In this instance, the interface Cu barrier layer 428 can beformed from such a material as, for example, SiN, SiON, SiCN or anorganic resin similarly as in the first working example. Further in thisinstance, the metal barrier layer for covering the W joining portion ispreferably configured from a multilayer film formed by laminating a Tifilm and a TiN film in this order from the W joining portion side, thatis, from a Ti/TiN laminated film. It is to be noted that, however, sinceW is a metal material less liable to react with oxygen, that is, lessliable to self-produce an interface barrier film, it is difficult to useW for the joining portions in the configuration of the second workingexample described hereinabove.

[Modification 5]

While, in the working examples and the modifications described above,metal films to which a signal is supplied are joined together along thejoining interface Sj, the present disclosure is not limited to this.Also in the case where metal films to which no signal is supplied arejoined together, the Cu—Cu joining technique described in connectionwith the working examples and the modifications can be applied.

For example, also in the case where dummy electrodes are joinedtogether, the Cu—Cu joining technique described hereinabove inconnection with the working examples and the modifications can beapplied. Further, also in the case where, for example, in a solid-stateimage pickup device, metal films of a sensor section and a logic circuitsection are joined together to form a light intercepting film, the Cu—Cujoining technique described in connection with the working examples andthe modifications can be applied.

Reference Example 1

In the second working example described above, the dimension or surfacearea of the surface of the first Cu joining portion 416 on the joininginterface Sj side and that of the second Cu joining portion 426 aredifferent from each other. However, the Cu—Cu joining techniquedescribed hereinabove in connection with the second working example canbe applied also to a semiconductor device wherein the surface shape anddimension of the first Cu joining portion on the joining interface Sjside and those of the second Cu joining portion are same as each other.

FIG. 27 shows an example of such an application as just described, thatis, a reference example 1. It is to be noted that FIG. 27 shows aschematic cross section of the semiconductor device 500 of the presentreference example 1 in the proximity of a joining interface Sj. It is tobe noted that, in the semiconductor device 500 of the present referenceexample shown in FIG. 27, like elements to those of the semiconductordevice 402 of the second working example shown in FIG. 17 are denoted bylike reference characters.

Referring to FIG. 27, the semiconductor device 500 of the presentreference example includes a first semiconductor member 501, a secondsemiconductor member 440, and an interface Cu barrier film 505. It is tobe noted that the second semiconductor member 440 in the semiconductordevice 500 of the present reference example has a configuration similarto that in the second working example described hereinabove withreference to FIG. 17, and therefore, overlapping description of thesecond semiconductor member 440 is omitted herein to avoid redundancy.

The first semiconductor member 501 includes a first semiconductor membernot shown, a first SiO2 film 411, a first Cu wiring line portion 412, afirst Cu barrier film 413, a first Cu diffusion preventing film 414, afirst interlayer insulating film 415, a first Cu joining portion 502, afirst Cu barrier layer 503 and a first Cu seed layer 504.

It is to be noted that, in the present example, the surface shape andthe dimension of the first Cu joining portion 502 on the joininginterface Sj side are made same as those of the second Cu joiningportion 426. The configuration of the other part of the firstsemiconductor member 501 is similar to that of the corresponding part ofthe first semiconductor member 430 in the second working example.

Also in the present example, the surface of the first semiconductormember 501 on the first Cu joining portion 502 side and the surface ofthe second semiconductor member 440 on the second Cu joining portion 426side are joined to each other to produce the semiconductor device 500similarly as in the second working example. Thereupon, if joiningmisalignment occurs between the two Cu joining portions, then a metalmaterial such as Mn, Mg, Ti or Al in each Cu seed layer selectivelyreacts with oxygen of the interlayer insulating film to which the Cuseed layer opposes across the joining interface Sj in an annealingprocess upon joining. As a result, an interface Cu barrier film 505 isformed in a region of the joining interface Sj across which the first Cujoining portion 502 and the second interlayer insulating film 425 opposeto each other and a region of the joining interface Sj across which thesecond Cu joining portion 426 and the first interlayer insulating film415 oppose to each other as shown in FIG. 27.

As described above, also in the semiconductor device 500 of the presentexample, the interface Cu barrier film 505 is provided in the region ofthe joining interface Sj across which the Cu joining portion of one ofthe semiconductor member and the interlayer insulating film of the othersemiconductor member. Therefore, also with the present example, effectssimilar to those achieved by the second working example are achieved.

Reference Example 2

In the reference example 1, the Cu—Cu joining technique describedhereinabove in connection with the second working example is applied toa semiconductor device wherein the surface shape and the dimension ofthe first Cu joining portion on the joining interface Sj side and thoseof the second Cu joining portion are same as each other. Here, anotherconfiguration example wherein the Cu—Cu joining technique describedhereinabove in connection with the first working example is furthercombined with the semiconductor device 500 of the reference example 1 isdescribed.

FIG. 28 shows an example of such an application as just described, thatis, a reference example 2. It is to be noted that FIG. 28 shows aschematic cross section of the semiconductor device 510 of the presentreference example 2 in the proximity of a joining interface Sj. It is tobe noted that, in the semiconductor device 510 of the present referenceexample shown in FIG. 28, like elements to those of the semiconductordevice 500 of the reference example 1 shown in FIG. 27 are denoted bylike reference characters.

Referring to FIG. 28, the semiconductor device 510 of the presentexample includes a first semiconductor member 501, a secondsemiconductor member 520, and a first interface Cu barrier film 521. Itis to be noted that the first semiconductor member 501 in thesemiconductor device 510 of the present reference example has aconfiguration similar to that in the reference example 1 describedhereinabove with reference to FIG. 27, and therefore, overlappingdescription of the first semiconductor member 501 is omitted herein toavoid redundancy.

The second semiconductor member 520 includes a second semiconductorsubstrate not shown, a second SiO2 layer 421, a second Cu wiring lineportion 422, a second Cu barrier film 423, a second Cu diffusionpreventing film 424, a second interlayer insulating film 425, a secondCu joining portion 426, a second Cu barrier layer 427, and a second Cuseed layer 441. Further, the second semiconductor member 520 includes asecond interface Cu barrier film 522.

As can be recognized from comparison between FIGS. 28 and 27, the secondsemiconductor member 520 in the present reference example is configuredsuch that the second interface Cu barrier film 522 is provided on thesecond interlayer insulating film 525 in the second semiconductor member440 of the reference example 1. Further, in the present example, thesecond interface Cu barrier film 522 is formed such that the surface ofthe second Cu joining portion 426 on the joining interface Sj side andthe surface of the second interface Cu barrier film 522 may besubstantially in flush with each other. It is to be noted that theconfiguration of the other part of the second semiconductor member 520than the second interface Cu barrier film 522 is similar to that of thecorresponding part of the second semiconductor member 440 of thereference example 1 described hereinabove.

Further, the second interface Cu barrier film 522 can be formed fromsuch a material as, for example, SiN, SiON, SiCN or an organic resinsimilarly to the interface Cu barrier layer 428 in the first workingexample. However, from a point of view of the close contactness with theCu film, it is preferable to form the second interface Cu barrier film522 from SiN.

Also in the present example, similarly as in the second working example,the semiconductor device 510 is produced by joining the surface of thefirst semiconductor member 501 on the first Cu joining portion 502 sideand the surface of the second semiconductor member 520 on the second Cujoining portion 426 side to each other. Thereupon, if misalignmentoccurs between the two Cu joining portions, then by an annealing processupon joining, a metal material such as Mn, Mg, Ti or Al in the Cu seedlayers selectively reacts with oxygen of the interlayer insulating filmwhich opposes to the Cu seed layers across the joining interface Sj. Asa result, a first interface Cu barrier film 521 is formed in a region ofthe joining interface Sj across which the Cu joining portion of one ofthe semiconductor members and the interlayer insulating film of theother semiconductor member oppose to each other.

However, in the present example, the second interface Cu barrier film522 is provided on the surface of the second semiconductor member 520 onthe joining interface Sj side as described hereinabove. Therefore, inthe present example, the first interface Cu barrier film 521 is formedin one of the region of the joining interface Sj across which the firstCu joining portion 502 and the second interlayer insulating film 425oppose to each other and the region of the joining interface Sj acrosswhich the second Cu joining portion 426 and the first interlayerinsulating film 415 oppose to each other. Further, the second interfaceCu barrier film 522 is disposed in the other of the region of thejoining interface Sj across which the first Cu joining portion 502 andthe second interlayer insulating film 425 oppose to each other and theregion of the joining interface Sj across which the second Cu joiningportion 426 and the first interlayer insulating film 415 oppose to eachother. In the example shown in FIG. 28, the second interface Cu barrierfilm 522 is provided in the region of the former joining interface Sj,and the first interface Cu barrier film 521 is provided in the region ofthe latter joining interface Sj.

As described above, also in the semiconductor device 510 of the presentexample, the first interface Cu barrier film 521 or the second interfaceCu barrier film 522 is provided in the region of the joining interfaceSj across which the Cu joining portion of one of the semiconductormembers and the interlayer insulating film of the other semiconductormember oppose to each other. Therefore, also with the present example,similar effects to those achieved by the first and second workingexamples can be achieved.

5. Forth Working Example

Usually, when a first semiconductor member and a second semiconductormember having Cu joining portions which have different areas from eachother are bonded to each other to carry out Cu—Cu joining, the Cujoining portion of one of the semiconductor member and an interlayerinsulating film of the other semiconductor member contact with eachother. FIG. 29 shows a schematic cross section in the proximity of ajoining interface in an example of the joining just described. It is tobe noted that, in the semiconductor device 650 shown in FIG. 29, likeelements to those in the semiconductor device 401 of the first workingexample described hereinabove with reference to FIG. 14 are denoted bylike reference characters.

Referring to FIG. 29, Cu diffuses from a first Cu joining portion 416having an area greater than that of a second Cu joining portion 426 intoa second interlayer insulating film 425 as indicated by dotted linearrow marks in FIG. 29 and thereby deteriorates an electriccharacteristic at the joining interface Sj and degrades the reliabilityof the Cu joining portions and the semiconductor device 650. Incontrast, in the working examples described above, an interface barrierfilm is formed along the joining interface between the first Cu joiningportion 416 and the second interlayer insulating film 425 and canthereby prevent diffusion of Cu from the first Cu joining portion 416into the second interlayer insulating film 425. Consequently, theproblem described above can be solved.

Further, as another technique for preventing diffusion of Cu through thejoining interface described above, a technique may be applicable whereina first semiconductor member and a second semiconductor member arebonded to each other in a state in which the surface of an interlayerinsulating film on the joining interface side of at least one of thefirst and second semiconductor members is retracted from the joiningside face of the Cu joining portion. In other words, also a techniquemay be applicable wherein the first and second semiconductor members arebonded to each other in a state in which the Cu joining portion of atleast one of the first and second semiconductor members is projectedtoward the joining interface side.

FIG. 30 shows a schematic cross section in the proximity of a joininginterface in the case where a first semiconductor member and a secondsemiconductor member are bonded to each other in a state in which Cujoining portions of both the first and second semiconductor members areprojected toward the joining interface side. It is to be noted that, inthe semiconductor device 660 shown in FIG. 30, like elements to those ofthe semiconductor device 401 of the first working example shown in FIG.14 are denoted by like reference characters.

In this instance, a gap is formed along the joining interface Sj betweenthe first semiconductor member 661 and the second semiconductor member662, particularly between a first interlayer insulating film 663 and asecond interlayer insulating film 664. Consequently, an air gap isformed between the second interlayer insulating film 664 and the firstCu joining portion 416, and diffusion of Cu from the first Cu joiningportion 416 into the second interlayer insulating film 664 is prevented.However, in this instance, external air enters the gap along the joininginterface Sj as indicated by outline arrow marks and contaminates thesurface of the first Cu joining portion 416. Consequently, an electriccharacteristic at the joining interface Sj is deteriorated and thereliability of the Cu joining portions and the semiconductor device isdegraded.

Therefore, in the fourth working example, a semiconductor device whereinan air gap is formed between a second interlayer insulating film and afirst Cu joining portion is configured such that it can prevent such aninfluence of external air as described above.

[Configuration of the Semiconductor Device]

FIGS. 31 and 32 show a general configuration of a semiconductor deviceaccording to a fourth working example. Particularly, FIG. 31 shows aschematic cross section of the semiconductor device according to thefourth working example in the proximity of a joining interface, and FIG.32 shows a schematic top plan in the proximity of the joining interfaceand illustrates an arrangement relationship of Cu joining portions andan air gap defined along the joining interface. It is to be noted that,in FIGS. 31 and 32, in order to simplify description, a configurationonly in the proximity of one joining interface is shown. Further, in thesemiconductor device 530 of the present working example shown in FIG.31, like elements to those of the semiconductor device 401 of the firstworking example shown in FIG. 14 are denoted by like referencecharacters.

Referring first to FIG. 31, the semiconductor device 530 includes afirst semiconductor member 531 which is a first semiconductor sectionand a second semiconductor member 532 which is a second semiconductorsection.

The first semiconductor member 531 includes a first semiconductorsubstrate not shown, a first SiO2 layer 411, a first Cu wiring lineportion 412, a first Cu barrier film 413, a first Cu diffusionpreventing film 414, a first interlayer insulating film 415, a first Cujoining portion 533 and a first Cu barrier layer 417.

As apparent from comparison between FIGS. 31 and 14, the firstsemiconductor member 531 in the present working example is configuredsuch that, on the surface area of the first semiconductor member 410 ofthe first example on the joining interface Sj side, a recessed portionis provided in the surface region of the first Cu joining portion 416opposing to the second interlayer insulating film 425. The configurationof the other part of the first semiconductor member 531 than theconfiguration just described is similar to that of the correspondingpart of the first semiconductor member 410 of the first working exampledescribed hereinabove.

The second semiconductor member 532 includes a second semiconductorsubstrate not shown, a second SiO2 layer 421, a second Cu wiring lineportion 422, a second Cu barrier film 423, a second Cu diffusionpreventing film 424, a second interlayer insulating film 425 and asecond Cu joining portion 426.

As apparent from comparison between FIGS. 31 and 14, the secondsemiconductor member 532 in the present working example is configuredsuch that the second semiconductor member 420 in the first workingexample does not include the interface Cu barrier film 428. Theconfiguration of the other part of the second semiconductor member 532than this is similar to that of the corresponding part of the secondsemiconductor member 420 in the first working example.

In the semiconductor device 530 in the present working example, in thesurface region of the first semiconductor member 531 on the joininginterface Sj side, a recessed portion 534 is provided in the surfaceregion of the first Cu joining portion 533 opposing to the secondinterlayer insulating film 425 of the second semiconductor member 532 asseen in FIG. 31. Consequently, a structure can be formed wherein an airgap is formed in a region along the joining interface Sj across whichthe first Cu joining portion 533 of the first semiconductor member 531and the second interlayer insulating film 425 of the secondsemiconductor member 532 oppose to each other and the first Cu joiningportion 533 does not contact directly with the second interlayerinsulating film 425.

In particular, in the semiconductor device 530 in the present workingexample, an interface barrier portion is configured from the recessedportion 534 of the first Cu joining portion 533 and the surface regionportion, that is, the face region portion, on the joining interface Sjside of the second semiconductor member 532 opposing to the recessedportion 534. Further, in the present working example, the air gapdefined by the recessed portion 534 of the first Cu joining portion 533and the surface of the second interlayer insulating film 425 on thejoining interface Sj side is placed in a state in which it is sealed byvarious films therearound as seen in FIG. 31.

[Fabrication Technique of the Semiconductor Device]

Now, a fabrication technique of the semiconductor device 530 in thepresent embodiment is described with reference to FIGS. 33A to 33D. Itis to be noted that FIGS. 33A and 33B show cross sections in theproximity of a Cu joining portion of semiconductor members produced atdifferent steps, and FIGS. 33C and 33D illustrate a manner of a joiningprocess of the first semiconductor member 531 and the secondsemiconductor member 532.

First, in the present working example, a first semiconductor member 531is produced as seen in FIG. 33A in a similar manner as at the productionstep of the first semiconductor member 410 in the first working exampledescribed hereinabove with reference to FIGS. 16A to 16F.

Further, in the present working example, a second semiconductor member532 is produced as seen in FIG. 33B in a similar manner as at theproduction step of the first semiconductor member 410 in the firstworking example described hereinabove with reference to FIGS. 16A to16F. It is to be noted, however, that, in this instance, at the step offorming an opening corresponding to a formation region of the second Cujoining portion 426 and the second Cu barrier layer 427 in the secondinterlayer insulating film 425 corresponding to the step of FIG. 16C,the opening diameter of the opening is set to approximately 1 to 95 μm.

Then, a reduction process is carried out for the surface of the firstsemiconductor member 531 on the first Cu joining portion 533 side andthe surface of the second semiconductor member 532 on the second Cujoining portion 426 side to remove an oxide film or oxides on thesurface of the Cu joining portions to expose clean Cu to the surface ofthe Cu joining portions. It is to be noted that, as the reductionprocess in this instance, a wet etching process in which solution ofdrug such as, for example, formic acid is used or a dry etching processin which plasma of, for example, Ar, NH3 or H2 is used is used.

Thereafter, the surface of the first semiconductor member 531 on thefirst Cu joining portion 533 side and the surface of the secondsemiconductor member 532 on the second Cu joining portion 426 side arecontacted with each other or bonded to each other as seen in FIG. 33C.

Then, in the state in which the first semiconductor member 531 and thesecond semiconductor member 532 are bonded to each other, the bondedmember is annealed using a heating apparatus or annealing apparatus suchas, for example, a hot plate or a RTA apparatus to join the first Cujoining portion 533 and the second Cu joining portion 426 to each otheras seen in FIG. 33D. In particular, the bonded member is heated atapproximately 100 to 400° C. for approximately five minutes to twohours, for example, in an N2 atmosphere of the atmospheric pressure orin vacuum.

In the present working example, the Cu film of the first Cu joiningportion 533 is further stiffened by the annealing process illustrated inFIG. 33D. It is to be noted that, on the joining interface Sj, thecontact region between the first Cu joining portion 533 and the secondinterlayer insulating film 425 is lower in close contacting force thanthe other region. Therefore, by the annealing process illustrated inFIG. 33D, the first Cu joining portion 533 in the contact regioncontracts and the surface of the first Cu joining portion 533 retreatsin a direction in which it is spaced away from the joining interface Sj.As a result, in the surface region of the first semiconductor member 531on the joining interface Sj, a recessed portion 534 is formed in thesurface region of the first Cu joining portion 533 opposing to thesecond interlayer insulating film 425 as seen in FIG. 33D.

In particular, by the annealing process illustrated in FIG. 33D, astructure is formed wherein an air gap is formed along the joininginterface Sj between the first Cu joining portion 533 and the secondinterlayer insulating film 425 and is sealed in the semiconductor device530 by various films therearound. It is to be noted that, in order toform the recessed portion 534 by the annealing process illustrated inFIG. 33D, preferably the annealing is carried out, for example, at atemperature higher than the annealing temperature of the annealingprocess carried out to form the Cu joining portions of fine film qualityupon production of the semiconductor members.

In the present working example, a Cu—Cu joining process is carried outin such a manner as described above. It is to be noted that the otherpart of the fabrication process of the semiconductor device 530 otherthan the joining step described above may be similar to that of thefabrication technique of a currently available semiconductor device suchas, for example, a solid-state image pickup device (refer to, forexample, Japanese Patent Laid-Open No. 2007-234725).

As described above, the semiconductor device 530 in the present workingexample is structured such that an air gap is formed along the joininginterface Sj between the first Cu joining portion 533 and the secondinterlayer insulating film 425 such that they do not contact directlywith each other. Therefore, also in the present working example,diffusion of Cu from the first Cu joining portion 533 into the secondinterlayer insulating film 425 can be prevented similarly as in thefirst working example. It is to be noted that, since the region of theair gap formed along the joining interface Sj is sufficiently small incomparison with the overall region of the joining interface Sj, theclose contact performance of the joining interface Sj in theconfiguration of the present working example is similar to that in theworking examples described hereinabove.

Further, in the semiconductor device 530 of the present working example,the air gap formed along the joining interface Sj between the first Cujoining portion 533 and the second interlayer insulating film 425 isplaced in a state in which it is sealed by various films therearound.Therefore, in the present working example, invasion of external air tothe Cu joining portions can be prevented, and the reliability of thesemiconductor device 530 can be assured.

6. Fifth Working Example

Another configuration example of a semiconductor device wherein an airgap is provided along a joining interface between a first Cu joiningportion of a first semiconductor member and a second interlayerinsulating film of a second semiconductor member is described as a fifthworking example.

[Configuration of the Semiconductor Device]

FIGS. 34 and 35 show a general configuration of a semiconductor deviceaccording to a fifth working example. Particularly, FIG. 34 shows aschematic cross section of the semiconductor device according to thefifth working example in the proximity of a joining interface, and FIG.35 shows a schematic top plan in the proximity of the joining interfaceand illustrates an arrangement relationship of Cu joining portions andinterface Cu barrier film to an air gap defined along the joininginterface. It is to be noted that, in FIGS. 34 and 35, in order tosimplify description, a configuration only in the proximity of onejoining interface is shown. Further, in the semiconductor device 540 ofthe present working example shown in FIG. 34, like elements to those ofthe semiconductor device 530 of the fourth working example shown in FIG.31 are denoted by like reference characters.

Referring first to FIG. 34, the semiconductor device 540 includes afirst semiconductor member 531 which is a first semiconductor sectionand a second semiconductor member 420 which is a second semiconductorsection.

The first semiconductor member 531 is similar in configuration to thatin the fourth working example described hereinabove with reference toFIG. 31. In particular, the first semiconductor member 531 is configuredsuch that, in the surface region on the joining interface Sj side of thefirst semiconductor member 410 in the first working example describedhereinabove with reference to FIG. 14, a recessed portion 534 isprovided in the surface region of the first Cu joining portion 533opposing to the second interlayer insulating film 425 of the secondsemiconductor member 420. Meanwhile, the second semiconductor member 420has a configuration similar to that in the first working exampledescribed hereinabove with reference to FIG. 14 in that the interface Cubarrier film 428 is provided on the surface of the second interlayerinsulating film 425 on the joining interface Sj side.

In the semiconductor device 540 in the present working example, in thesurface region of the first semiconductor member 531 on the joininginterface Sj, the recessed portion 534 is provided in the surface regionof the first Cu joining portion 533 opposing to the interface Cu barrierfilm 428 of the second semiconductor member 420 as described above.Consequently, an air gap is formed along the joining interface Sj acrosswhich the first Cu joining portion 533 of the first semiconductor member531 and the interface Cu barrier film 428 of the second semiconductormember 420 oppose to each other. Further, in the present workingexample, the air gap defined by the recessed portion 534 of the first Cujoining portion 533 and the surface of the interface Cu barrier film 428on the joining interface Sj side is placed in a state in which it issealed by various films therearound as seen in FIG. 34.

In particular, also in the present working example, an interface barrierportion is configured from the recessed portion 534 of the first Cujoining portion 533 and the surface region portion or face regionportion on the joining interface Sj side of the second semiconductormember 420 opposing to the recessed portion 534. Further, in the presentworking example, diffusion of Cu from the first Cu joining portion 533into the second interlayer insulating film 425 is prevented by the airgap formed in the surface barrier portion and also by the interface Cubarrier film 428.

[Fabrication Technique of the Semiconductor Device]

Now, a fabrication technique of the semiconductor device 540 in thepresent working example is described with reference to FIGS. 36A to 36D.It is to be noted that FIGS. 36A and 36B show schematic cross sectionsin the proximity of a Cu joining portion of semiconductor membersproduced at different steps, and FIGS. 36C and 36D illustrate a mannerof a joining process between the first semiconductor member 531 and thesecond semiconductor member 420.

First, in the present working example, a first semiconductor member 531is produced as seen in FIG. 36A in a similar manner as at the productionstep of the first semiconductor member 410 in the first working exampledescribed hereinabove with reference to FIGS. 16A to 16F.

Further, in the present working example, a second semiconductor member420 is produced as seen in FIG. 36B in a similar manner as at theproduction step of the second semiconductor member 420 in the firstworking example described hereinabove with reference to FIGS. 16G to16L. However, in the present working example, the film thickness of theinterface Cu barrier film 428 which may be, for example, a SiN film or aSiCN film is approximately 10 to 100 nm, and an interface Cu barrierfilm 428 is formed by a CVD method or a spin coating method. Further, inthe present working example, at the step of forming an openingcorresponding to a formation region for the second Cu joining portion426 and the second Cu barrier layer 427 in the second interlayerinsulating film 425 corresponding to the step of FIG. 16I, the openingdiameter of the opening is set to approximately 4 to 100 μm.

Then, a reduction process is carried out for the surface of the firstsemiconductor member 531 on the first Cu joining portion 533 side andthe surface of the second semiconductor member 420 on the second Cujoining portion 426 side to remove an oxide film or oxides on thesurface of the Cu joining portions to expose clean Cu to the surface ofthe Cu joining portions. It is to be noted that, as the reductionprocess in this instance, a wet etching process in which solution ofdrug such as, for example, formic acid is used or a dry etching processin which plasma of, for example, Ar, NH3 or H2 is used is used.

Thereafter, the surface of the first semiconductor member 531 on thefirst Cu joining portion 533 side and the surface of the secondsemiconductor member 420 on the second Cu joining portion 426 side arecontacted with each other or bonded to each other as seen in FIG. 36C.

Then, in the state in which the first semiconductor member 531 and thesecond semiconductor member 420 are bonded to each other, the bondedmember is annealed using a heating apparatus or annealing apparatus suchas, for example, a hot plate or a RTA apparatus to join the first Cujoining portion 533 and the second Cu joining portion 426 to each otheras seen in FIG. 36D. In particular, the bonded member is heated atapproximately 100 to 400° C. for approximately five minutes to twohours, for example, in an N2 atmosphere of the atmospheric pressure orin vacuum.

In the present working example, the Cu film of the first Cu joiningportion 533 is further stiffened by the annealing process illustrated inFIG. 36D similarly as in the fourth working example describedhereinabove. Thereupon, in the contact region between the first Cujoining portion 533 and the interface Cu barrier film 428 on the joininginterface Sj, the first Cu joining portion 533 contracts and the surfaceof the first Cu joining portion 533 retreats in a direction in which itis spaced away from the joining interface Sj. As a result, in thesurface region of the first semiconductor member 531 on the joininginterface Sj, a recessed portion 534 is formed in the surface region ofthe first Cu joining portion 533 opposing to the interface Cu barrierfilm 428 as seen in FIG. 36D.

In particular, by the annealing process illustrated in FIG. 36D, astructure is formed wherein an air gap is formed along the joininginterface Sj between the first Cu joining portion 533 and the interfaceCu barrier film 428 and is sealed in the semiconductor device 540 byvarious films therearound. It is to be noted that, in order to form therecessed portion 534 by the annealing process illustrated in FIG. 36D,preferably the annealing is carried out, for example, at a temperaturehigher than the annealing temperature of the annealing process carriedout to form the Cu joining portions of fine film quality upon productionof the semiconductor members.

In the present working example, a Cu—Cu joining process is carried outin such a manner as described above. It is to be noted that the otherpart of the fabrication process of the semiconductor device 540 otherthan the joining step described above may be similar to that of thefabrication technique of a currently available semiconductor device suchas, for example, a solid-state image pickup device (refer to, forexample, Japanese Patent Laid-Open No. 2007-234725).

As described above, the semiconductor device 540 in the present workingexample is structured such that an air gap is formed in a region alongthe joining interface Sj between the first Cu joining portion 533 andthe interface Cu barrier film 428 such that they do not contact directlywith each other. Further, in the present working example, the interfaceCu barrier film 428 is formed in the region opposing to the recessedportion 534 of the first Cu joining portion 533. Therefore, in thepresent working example, diffusion of Cu from the first Cu joiningportion 533 into the second interlayer insulating film 425 can beprevented with a higher degree of certainty.

Further, in the semiconductor device 540 of the present working example,the air gap formed along the joining interface Sj between the first Cujoining portion 533 and the interface Cu barrier film 428 is placed in astate in which it is sealed by various films therearound. Therefore, inthe present working example, invasion of external air to the Cu joiningportions can be prevented similarly as in the fourth working exampledescribed above, and the reliability of the semiconductor device 540 canbe assured.

It is to be noted that, while, in the present working example, theformation technique of an interface barrier portion describedhereinabove in connection with the fourth working example is applied tothe semiconductor device 401 of the first working example describedhereinabove with reference to FIG. 14, the present disclosure is notlimited to this. For example, the formation technique of an interfacebarrier portion described hereinabove in connection with the fourthworking example may be applied also to the semiconductor device 402 ofthe second working example described hereinabove with reference to FIG.17 or the semiconductor device 403 of the third working exampledescribed hereinabove with reference to FIG. 20. Further, the formationtechnique of an interface barrier portion described hereinabove inconnection with the fourth working example may be applied, for example,also to the various semiconductor devices of the modifications describedhereinabove with reference to FIGS. 23 to 26 and so forth.

Further, the formation technique of an interface barrier portiondescribed hereinabove in connection with the fourth working example maybe applied also to the semiconductor device of the various referenceexamples described hereinabove with reference to FIGS. 27 and 34.However, in this instance, a recessed portion is formed not only on thesurface region of the first Cu joining portion opposing to the secondinterlayer insulation film but also in the surface region of the secondCu joining portion opposing to the first interlayer insulating filmalong the joining interface Sj.

7. Applications

The semiconductor devices and the fabrication techniques for thesemiconductor device, that is, the Cu—Cu joining techniques, describedhereinabove in connection with the various working examples andmodifications can be applied to various electronic apparatus whichrequire bonding of two substrates to carry out a Cu—Cu joining processupon fabrication. Particularly, the Cu—Cu joining techniques of theworking examples and the modifications described hereinabove can beapplied suitably to fabrication of, for example, a solid-state imagepickup device.

[Application 1]

FIG. 37 shows an example of a configuration of a semiconductor imagesensor module to which the semiconductor devices and the fabricationtechniques for the semiconductor device described hereinabove inconnection with the various working examples and modifications can beapplied. Referring to FIG. 37, the semiconductor image sensor module 700is configured from a first semiconductor chip 701 and a secondsemiconductor chip 702 joined together.

The first semiconductor chip 701 has a photodiode formation region 703,a transistor formation region 704 and an analog/digital converter array705 built therein. The transistor formation region 704 and theanalog/digital converter array 705 are laminated in order on thephotodiode formation region 703.

Penetrating contact portions 706 are formed in the analog/digitalconverter array 705. Each of the penetrating contact portions 706 isformed such that it is exposed at one end portion thereof to the surfaceof the analog/digital converter array 705 on the second semiconductorchip 702 side.

Meanwhile, the second semiconductor chip 702 is configured from a memoryarray and has contact portions 707 formed in the inside thereof. Each ofthe contact portions 707 is formed such that it is exposed at one endportion thereof to the surface of the second semiconductor chip 702 onthe first semiconductor chip 701 side.

Then, the penetrating contact portions 706 and the contact portions 707are heated and contact bonded to each other in a state in which they areabutted with each other to join the first semiconductor chip 701 and thesecond semiconductor chip 702 to each other thereby to produce thesemiconductor image sensor module 700. With the semiconductor imagesensor module 700 having such a configuration as described above, thenumber of pixels per unit area can be increased and the thickness can bereduced.

In the semiconductor image sensor module 700 of the present application,the Cu—Cu joining techniques of the working examples and themodifications described hereinabove can be applied, for example, to thejoining step between the first semiconductor chip 701 and the secondsemiconductor chip 702. In this instance, the reliability of the joininginterface between the first semiconductor chip 701 and the secondsemiconductor chip 702 can be improved further.

[Application 2]

FIG. 38 shows a schematic cross section of part of a solid-state imagepickup device of the backside illumination type to which thesemiconductor devices and the fabrication techniques for thesemiconductor device, that is, the Cu—Cu joining techniques, describedhereinabove in connection with the various working examples andmodifications can be applied.

Referring to FIG. 38, the solid-state image pickup device 800 shown isconfigured by joining a first semiconductor substrate 810 in the form ofa partially fabricated item including a pixel array and a secondsemiconductor substrate 820 in the form of a partially fabricated itemincluding a logic circuit to each other. It is to be noted that, in thesolid-state image pickup device 800 shown in FIG. 38, a flattening film830, an on-chip color filter 831 and an on-chip microlens array 832 arelaminated in this order on a face of the first semiconductor substrate810 opposite to the second semiconductor substrate 820.

The first semiconductor substrate 810 includes a semiconductor wellregion 811 of the P type and a multilayer wiring line layer 812. Thesemiconductor well region 811 is disposed on the first semiconductorsubstrate 810 on the flattening film 830 side. In the semiconductor wellregion 811, for example, a photodiode (PD), a floating diffusion (FD),MOS transistors (Tr1 and Tr2) which configure a pixel and MOStransistors (Tr3 and Tr4) which configure a control circuit are formed.Meanwhile, in the multilayer wiring line layer 812, a plurality of metalwiring lines 814 are formed with an interlayer insulating film 813interposed therebetween and connecting conductors 815 are formed in theinterlayer insulating film 813 in order to connect the metal wiringlines 814 and corresponding MOS transistors to each other.

Meanwhile, the second semiconductor substrate 820 includes asemiconductor well region 821 formed, for example, in the surface of asilicon substrate and a multilayer wiring line layer 822 formed in thesemiconductor well region 821 on the first semiconductor substrate 810side. In the semiconductor well region 821, MOS transistors (Tr6, Tr7and Tr8) which configure a logic circuit are formed. Meanwhile, in themultilayer wiring line layer 822, a plurality of metal wiring lines 824are formed with an interlayer insulating film 823 interposedtherebetween and connecting conductors 825 are formed in the interlayerinsulating film 823 in order to connect the metal wiring lines 824 tocorresponding MOS transistors.

The Cu—Cu joining techniques of the working examples and themodifications according to the present disclosure described hereinabovecan be applied also to the solid-state image pickup device 800 of thebackside illumination type of the configuration described above.

Fourth Embodiment 1. Outline of the Semiconductor Device

An outline of a configuration of a joining electrode of a semiconductordevice is described.

FIG. 39 shows a general configuration of a joining electrode andparticularly shows a cross sectional configuration of a joining portionincluding a joining electrode.

A first joining portion 910 is formed on a semiconductor substrate notshown. The first joining portion 910 includes a first wiring line layer912, and a first joining electrode 911 connected to the first wiringline layer 912 through a via 913.

The first wiring line layer 912 is formed in a interlayer insulatinglayer 919. An interlayer insulating layer 17 is formed on the interlayerinsulating layer 919 with an intermediate layer 918 interposedtherebetween. Another interlayer insulating layer 915 is provided on theinterlayer insulating layer 17 with an intermediate layer 916 interposedtherebetween.

The first joining electrode 911 is formed in the interlayer insulatinglayer 915, and the surface of the first joining electrode 911 is exposedto the surface of the interlayer insulating layer 915. This exposed faceis formed in flush with the surface of the interlayer insulating layer915.

The first wiring line layer 912 and the first joining electrode 911 areelectrically connected to each other through the via 913 which extendsthrough the intermediate layer 916, interlayer insulating layer 917 andintermediate layer 918.

A barrier metal layer 914 for preventing diffusion of an electrodematerial into an insulating layer is provided between the first joiningelectrode 911 and via 913 and the interlayer insulating layers 915 and917 and intermediate layer 916. Further, another barrier metal layer 931is provided between the first wiring line layer 912 and the interlayerinsulating layer 919.

A second joining portion 920 is formed on a semiconductor substrate notshown similarly to the first joining portion 910 described hereinabove.The second joining portion 920 includes a second wiring line layer 922and a second joining electrode 921 connected to the second wiring linelayer 922 through a via 923.

The second wiring line layer 922 is formed in a interlayer insulatinglayer 929. Another interlayer insulating layer 927 is formed on theinterlayer insulating layer 929 with an intermediate layer 928interposed therebetween. A further interlayer insulating layer 925 isprovided on the interlayer insulating layer 927 with an intermediatelayer 926 interposed therebetween.

The second joining electrode 921 is formed in the interlayer insulatinglayer 925 such that the surface thereof is exposed from the surface ofthe interlayer insulating layer 925. This exposed face is formed inflush with the surface of the interlayer insulating layer 925.

The second wiring line layer 922 and the second joining electrode 921are electrically connected to each other through the via 923 extendingthrough the intermediate layer 926, interlayer insulating layer 927 andintermediate layer 928.

A barrier metal layer 924 for preventing diffusion of an electrodematerial into an insulating layer is provided between the second joiningelectrode 921 and via 923 and the interlayer insulating layers 925 and927 and intermediate layer 926. Another barrier metal layer 932 isprovided between the second wiring line layer 922 and the interlayerinsulating layer 929.

As described above, the first joining portion 910 and the second joiningportion 920 are bonded to each other in the state in which the firstjoining electrode 911 and the second joining electrode 921 are joinedtogether.

Further, the first joining electrode 911 and the second joiningelectrode 921 are designed such that the area of one of them is greaterthan that of the other of them such that, even if the joining positionbetween them is displaced, no difference occurs with the joining areabetween them in order to assure high joining reliability. With theconfiguration shown in FIG. 39, since the second joining electrode 921has the greater area, connection reliability against the positionaldisplacement is assured.

In the configuration shown in FIG. 39, since the first joining electrode911 and the second joining electrode 921 have an area differencetherebetween as described hereinabove, the second joining electrode 921having a greater area has, on the surface thereof, a contacting portion933 which contacts directly with the interlayer insulating layer 915 ofthe first joining portion 910.

This contacting portion 933 contacts at a metal layer of Cu or the likethereof directly with the interlayer insulating layer 915.

Further, since SiO2 which configures the interlayer insulating layer 915and so forth generally has a nature that it is liable to absorbmoisture, water (H2O) is liable to be included in the layers. Further, alow-k (k<2.4) material used for high performance devices in recent yearshas a further high moisture absorbing property.

Therefore, on the contacting portion 933 on which the second joiningelectrode 921 and the interlayer insulating layer 915 contact directlywith each other, water 930 included in the interlayer insulating layer915 and so forth and the second joining electrode 921 contact with eachother. In this instance, there is the possibility that the metal such asCu which configures the second joining electrode 921 may corrode.

As described above, in a semiconductor device of the configurationwherein semiconductor substrates contact at joining electrodes of metalthereof with each other, corrosion of the joining electrodes by waterincluded in the interlayer insulating layers occurs. If the joiningelectrodes are corroded by water, then this gives rise to increase inresistance, failure in connection and so forth, which make a cause ofobstruction to a normal function of the semiconductor devices.

Therefore, for the semiconductor devices joined together at the joiningelectrodes, a configuration for preventing corrosion of the joiningelectrodes by water included in the interlayer insulating layers isdemanded.

2. Embodiment of the Semiconductor Device

In the following, a semiconductor device according to the presentembodiment having a joining electrode is described.

FIGS. 40A and 40B show a general configuration of a semiconductor devicewhich includes a joining electrode according to the present embodiment.In particular, FIG. 40A shows a general configuration of thesemiconductor device in the proximity of a joining electrode region ofthe semiconductor device of the present embodiment and FIG. 40B shows atop plan of a joining face 950 of a first joining portion 940 shown inFIG. 40A. It is to be noted that FIGS. 40A and 40B only show a generalconfiguration in the proximity of a formation region of a joiningelectrode while components provided around the semiconductor substrateson which the joining electrodes are formed and the joining electrodesare omitted.

Referring first to FIG. 40A, a semiconductor device is formed wherein afirst joining portion 940 and a second joining portion 960 are joinedtogether with electrode formation faces thereof opposed to each other.

The first joining portion 940 includes a first joining electrode 941, asecond joining electrode 942 and a third joining electrode 943 on ajoining face 950. Meanwhile, the second joining portion 960 includes afourth joining electrode 961, a fifth joining electrode 962 and a sixthjoining electrode 963 on the joining face 950.

The first joining electrode 941 of the first joining portion 940 and thefourth joining electrode 961 of the second joining portion 960 arejoined together. Further, the second joining electrode 942 and the fifthjoining electrode 962 are joined together, and the third joiningelectrode 943 and the sixth joining electrode 963 are joined together.

[Insulating Layer]

Each of the first joining portion 940 and the second joining portion 960is configured from a plurality of wiring line layers and insulatinglayers laminated on each other.

The insulating layers of the first joining portion 940 include a firstinterlayer insulating layer 951, a first intermediate layer 952, asecond interlayer insulating layer 953, a second intermediate layer 954and a third interlayer insulating layer 955 laminated in this order fromthe joining face 950 side. Meanwhile, the insulating layers of thesecond joining portion 960 include a fourth interlayer insulating layer971, a third intermediate layer 972, a fifth interlayer insulating layer973, a fourth intermediate layer 974 and a sixth interlayer insulatinglayer 975 laminated in this order from the joining face 950 side.

[Conductor Layer: First Joining Portion]

The first joining electrode 941, second joining electrode 942 and thirdjoining electrode 943 of the first joining portion 940 are formed in thefirst interlayer insulating layer 951. The first joining electrode 941,second joining electrode 942 and third joining electrode 943 are exposedat the surface thereof to the joining face 950 and formed in flush withthe first interlayer insulating layer 951.

A first wiring line 946, a second wiring line 947 and a third wiringline 948 are formed at positions in the third interlayer insulatinglayer 955 in a contacting relationship with the second intermediatelayer 954.

The first joining electrode 941 and the first wiring line 946 areelectrically connected to each other through a first via 956 extendingthrough the first intermediate layer 952, second interlayer insulatinglayer 953 and second intermediate layer 954. Similarly, the secondjoining electrode 942 and the second wiring line 947 are electricallyconnected to each other through a second via 957. The third joiningelectrode 943 and the third wiring line 948 are electrically connectedto each other through a third via 958.

Further, a barrier metal layer 941A for preventing diffusion of thefirst joining electrode 941 into the first interlayer insulating layer951 is provided between the first joining electrode 941 and the firstinterlayer insulating layer 951. Meanwhile, barrier metal layers 942Aand 943A are provided between the second joining electrode 942 and thirdjoining electrode 943 and the first interlayer insulating layer 951.Further, a barrier metal layer 946A is provided between the first wiringline 946 and the third interlayer insulating layer 955; a barrier metallayer 947A is provided between the second wiring line 947 and the thirdinterlayer insulating layer 955; and a barrier metal layer 948A isprovided between the third wiring line 948 and the third interlayerinsulating layer 955.

Further, barrier metal layers 956A, 957A and 958A are provided betweenthe first, second and third vias 956, 957 and 958 and the firstintermediate layer 952, second interlayer insulating layer 953 andsecond intermediate layer 954, respectively. The first, second and thirdvias 956, 957 and 958 are connected to the first, second and thirdwiring lines 946, 947 and 948 through the barrier metal layers 956A,957A and 958A, respectively.

[Conductor Layer: Second Joining Portion]

The fourth joining electrode 961, fifth joining electrode 962 and sixthjoining electrode 963 of the second joining portion 960 are formed inthe fourth interlayer insulating layer 971. The fourth joining electrode961, fifth joining electrode 962 and sixth joining electrode 963 areexposed at the surface thereof to the joining face 950 and formed inflush with the fourth interlayer insulating layer 971.

A fourth wiring line 966, a fifth wiring line 967 and a sixth wiringline 968 are formed at positions in the sixth interlayer insulatinglayer 975 in a contacting relationship with the fourth intermediatelayer 974.

The fourth joining electrode 961 and the fourth wiring line 966 areelectrically connected to each other through a fourth via 976 extendingthrough the third intermediate layer 972, fifth interlayer insulatinglayer 973 and fourth intermediate layer 974. Similarly, the fifthjoining electrode 962 and the fifth wiring line 967 are electricallyconnected to each other through a fifth via 977. The sixth joiningelectrode 963 and the sixth wiring line 968 are electrically connectedto each other through a sixth via 978.

A barrier metal layer 961A for preventing diffusion of the fourthjoining electrode 961 into the fourth interlayer insulating layer 971 isprovided between the fourth joining electrode 961 and the fourthinterlayer insulating layer 971. Further, barrier metal layers 962A and963A are provided between the fifth and sixth joining electrodes 962 and963 and the fourth interlayer insulating layer 971, respectively.Further, a barrier metal layer 966A is provided between the fourthwiring line 966 and the sixth interlayer insulating layer 975; a barriermetal layer 967A is provided between the fifth wiring line 967 and thesixth interlayer insulating layer 975; and a barrier metal layer 968A isprovided between the sixth wiring line 968 and the sixth interlayerinsulating layer 975.

Also between the fourth, fifth and sixth vias 976, 977 and 978 and thethird intermediate layer 972, fifth interlayer insulating layer 973 andfourth intermediate layer 974, barrier metal layers 976A, 977A and 978Aare provided respectively. The fourth, fifth and sixth vias 976, 977 and978 are connected to the fourth, fifth and sixth wiring lines 966, 967and 968 through the barrier metal layers 976A, 977A and 978A,respectively.

[Material]

The first, second, third, fourth, fifth and sixth wiring lines 946, 947,948, 966, 967 and 968 are formed from a material used popularly forwiring lines of a semiconductor device such as, for example, Al or Cu.

Meanwhile, the first, second, third, fourth, fifth and sixth joiningelectrodes 941, 942, 943, 961, 962 and 963 are formed from a dielectricmaterial which allows joining of a semiconductor substrate thereto suchas, for example, Cu.

The barrier metal layers are formed from a material which is usedpopularly for barrier metal layers in a semiconductor device such as,for example, Ta, Ti, Ru, TaN or TiN.

The first, second, third, fourth, fifth and sixth interlayer insulatinglayers 951, 953, 955, 971, 973 and 975 are configured, for example, fromSiO2, organic silicon-based polymer represented by fluorine-containingsilicon oxide (FSG) or polyallyl ether (PAE), an inorganic materialrepresented by hydrosilsesquioxane (HSQ) or methylsilsesquioxane (MSQ),and particularly from a low-dielectric constant (Low-k) material havinga relative dielectric constant of approximately 2.7 or less.

As seen in FIG. 40A, the first to sixth interlayer insulating layers951, 953, 955, 971, 973 and 975 are liable to include water (H2O) 970 bymoisture absorption of the insulating layers.

The first, second, third and fourth intermediate layers 952, 954, 972and 974 are configured from a material used popularly for a diffusionpreventing layer for a metal material which configures wiring lines andso forth in a semiconductor device. Further, the intermediate layers arehigh density insulating layers which are less likely to allow water 970included in the interlayer insulating layers to penetrate therethrough.Further, such high density insulating layers serving as diffusionpreventing layers as just described are configured from P—SiN of arelative dielectric constant of 4 to 7 formed, for example, by a spincoating method or a CVD method or SiCN or the like of a relativedielectric constant equal to or lower than 4 in which C is contained.

[Joining Portion]

As described above, a semiconductor device is configured whereinsemiconductor substrates are joined together in the state in which thefirst, second and third joining electrodes 941, 942 and 943 and thefourth, fifth and sixth joining electrodes 961, 962 and 963 are joinedtogether.

Further, as seen in FIG. 40A, the joining electrode of the first joiningportion 940 and the joining electrode of the second joining portion 960are configured such that the area of one of them is greater in order toassure joining reliability. By this configuration, also when the joiningposition is displaced, the joining area between the electrodes does notvary.

In the configuration shown in FIG. 40A, the second joining electrode942, fourth joining electrode 961 and sixth joining electrode 963 areformed with a greater area than the respective opposing joiningelectrodes. Therefore, on the second joining electrode 942, a contactingportion 949 which contacts directly with the fourth interlayerinsulating layer 971 is formed. Further, on the surface of the fourthjoining electrode 961 and the sixth joining electrode 963, contactingportions 969 and 979 which contact directly with the first interlayerinsulating layer 951 are formed, respectively.

[Protective Layer]

The first joining portion 940 includes a first protective layer 944around the first joining electrode 941. The first joining portion 940further includes a second protective layer 945 which surrounds theperiphery of the second joining electrode 942 and the third joiningelectrode 943.

The first protective layer 944 and the second protective layer 945 areformed from a single layer which surrounds the periphery of the firstjoining electrode 941 as seen in FIG. 40B. Further, as shown in FIG.40A, the first protective layer 944 is formed in a recessed portion of adepth with which it extends from the joining face 950 of the firstjoining portion 940 through the first interlayer insulating layer 951 tothe first intermediate layer 952. The second protective layer 945 isformed in a recessed portion of a depth with which it extends from thejoining face 950 of the first joining portion 940 through the firstinterlayer insulating layer 951, first intermediate layer 952 and secondinterlayer insulating layer 953 to the second intermediate layer 954.

Further, as shown in FIG. 40A, the second joining portion 960 has athird protective layer 964 provided thereon at a position correspondingto the first protective layer 944 described hereinabove. Further, thesecond joining portion 960 has a fourth protective layer 965 providedthereon at a position corresponding to the second protective layer 945.

The third protective layer 964 is formed in a recessed portion of adepth with which it surrounds the periphery of the fourth joiningelectrode 961 and extends from the joining face 950 of the secondjoining portion 960 through the fourth interlayer insulating layer 971to the third intermediate layer 972.

The fourth protective layer 965 is formed in a recessed portion of adepth with which it surrounds the periphery of the fifth joiningelectrode 962 and the sixth joining electrode 963 and extends from thejoining face 950 of the second joining portion 960 through the fourthinterlayer insulating layer 971 to the third intermediate layer 972.

The first protective layer 944 and the third protective layer 964 areprovided at positions at which they contact with each other along thejoining face 950. By this configuration, the joining portions of thefirst joining electrode 941 and the fourth joining electrode 961 aresurrounded by the first protective layer 944, third protective layer964, first intermediate layer 952 and third intermediate layer 972.

Further, the second protective layer 945 and the fourth protective layer965 are provided at positions at which they contact with each otheralong the joining face 950. Therefore, the joining portions of thesecond joining electrode 942 and the fifth joining electrode 962 and thejoining portions of the third joining electrode 943 and the sixthjoining electrode 963 are surrounded by the second protective layer 945,fourth protective layer 965, second intermediate layer 954 and thirdintermediate layer 972.

The first, second, third and fourth protective layers, 944, 945, 964 and965 are formed from a material similar to that of the barrier metallayers described hereinabove, and for example, from Ta, Ti, Ru, TaN orTiN.

[Protective Layer: Action]

As described hereinabove, SiO2, a low-k material or the like applied tothe first interlayer insulating layer 951, fourth interlayer insulatinglayer 971 or the like has a nature that it is liable to absorb moisture.Particularly if interlayer insulating layers are joined together using aplasma joining method, then water is generated on the joining faces bysurface treatment and heat treatment of the insulating layers.Therefore, water (H2O) 970 is liable to be included in the firstinterlayer insulating layer 951, fourth interlayer insulating layer 971or the like by moisture absorption of the insulating layer material.

In the configuration of the semiconductor device of the presentembodiment, the first, second, third and fourth protective layers 944,945, 964 and 965 are provided around the joining electrodes. If theprotective layers are configured from a material similar to that of thebarrier metal layers, then penetration of water 970 included in theinsulating layers can be prevented. Further, the first intermediatelayer 952 and the third intermediate layer 972 are configured from ahigh density insulating layer of P—SiN or the like which is less liableto allow water 970 to penetrate therethrough.

Therefore, the water 970 included in the first interlayer insulatinglayer 951 or the fourth interlayer insulating layer 971 can beintercepted by the first protective layer 944, third protective layer964, first intermediate layer 952 and third intermediate layer 972.

Further, the water 970 included in the first interlayer insulating layer951 or the fourth interlayer insulating layer 971 can be intercepted bythe second protective layer 945, fourth protective layer 965, secondintermediate layer 954 and third intermediate layer 972.

By the configuration described above, contact of water 970 with thecontacting portion 969 between the fourth joining electrode 961 and thefirst interlayer insulating layer 951 can be suppressed by the joiningportion of the first joining electrode 941 and the fourth joiningelectrode 961. Similarly, contact of water 970 with the contactingportion 949 between the second joining electrode 942 and the fourthinterlayer insulating layer 971 can be suppressed by the joining portionbetween the second joining electrode 942 and the fifth joining electrode962. Further, contact of water 970 with the contacting portion 979between the sixth joining electrode 963 and the first interlayerinsulating layer 951 can be suppressed by the joining portion betweenthe third joining electrode 943 and the sixth joining electrode 963.

It is to be noted that, in the configuration described above, thecontacting portion 969 of the fourth joining electrode 961 contacts withwater 970 included in the first interlayer insulating layer 951 in aregion surrounded by the first protective layer 944, third protectivelayer 964, first intermediate layer 952, and third intermediate layer972. Therefore, the distance between the first joining electrode 941 andthe first protective layer 944 and the distance between the fourthjoining electrode 961 and the third protective layer 964 are preferablyset as short as possible. For example, the distances are set to thesmallest distance which is permitted in design rules for wiring so thatthe region in which an insulating layer can exist is minimized within aregion surrounded by the first protective layer 944, third protectivelayer 964 and so forth. The smallest distance between a joiningelectrode and a protective layer can be set to approximately 50 nm inthe minimum, and can be set to 2 to 4 μm in design rules for a popularsemiconductor device.

Also the contacting portion 949 of the second joining electrode 942 orthe contacting portion 979 of the sixth joining electrode 963 contactswith water 970 included in the first interlayer insulating layer 951 andthe fourth interlayer insulating layer 971 in the region of the thirdprotective layer 964, fourth protective layer 965 and so forth.Therefore, it is preferable to position the second protective layer 945and the fourth protective layer 965 as near as possible to the secondjoining electrode 942 and the sixth joining electrode 963, respectively,in accordance with design rules for wiring.

Further, it is desirable for a protective layer which surrounds ajoining electrode to be formed in such a manner as to screen at least aninsulating layer made of a material which is liable to absorb moisture.Therefore, the protective layer is preferably formed to a depth from thesurface of an interlayer insulating layer in which the joining electrodeis provided, that is, from the joining face, to an insulating layer onthe interlayer insulating layer, that is, to an intermediate layer.

Further, a protective layer may be formed to a position deeper than aninterlayer insulating layer in which a joining electrode is formed. Forexample, a protective layer may be formed so as to extend from thejoining face 950 through the first interlayer insulating layer 951,first intermediate layer 952 and second interlayer insulating layer 953to a position at which it contacts with the second intermediate layer954 like the second protective layer 945. According to the configurationof the second protective layer 945, since water in the second interlayerinsulating layer 953 can be intercepted, water 970 which may penetratethe first intermediate layer 952 from the second interlayer insulatinglayer 953 can be prevented.

Further, since the width of one of the protective layers which contactwith each other is set greater than that of the other protective layeralong the joining face 950, even if displacement of the joining positionof the semiconductor substrates occurs, connection reliability betweenthe protective layers can be assured. In the configuration of thesemiconductor device of the present embodiment shown in FIG. 40A, thewidth of the third protective layer 964 and the fourth protective layer965 on the joining face is greater than that of the first protectivelayer 944 and the second protective layer 945.

In particular, the third protective layer 964 and the first protectivelayer 944 are configured such that the joining electrode side, that is,the inner side, of the third protective layer 964 is positioned nearerto the joining electrode than the first protective layer 944 and theopposite side to the joining electrode of the third protective layer964, that is, the outer side of the third protective layer 964, ispositioned farther from the joining electrode than the first protectivelayer 944. In this manner, by setting the width of the third protectivelayer 964 greater, even when displacement occurs with the joiningposition, the first protective layer 944 contacts with the thirdprotective layer 964 within the width of the third protective layer 964.

Further, the fourth protective layer 965 and the second protective layer945 are configured such that the joining electrode side, that is, theinner side, of the fourth protective layer 965 is positioned nearer tothe joining electrode than the second protective layer 945 and theopposite side to the joining electrode of the fourth protective layer965, that is, the outer side of the fourth protective layer 965, ispositioned farther from the joining electrode than the second protectivelayer 945. In this manner, by setting the width of the fourth protectivelayer 965 greater, even when displacement occurs with the joiningposition, the second protective layer 945 contacts with the fourthprotective layer 965 within the width of the fourth protective layer965.

By the configuration described above, connection reliability of theprotective layers against positional displacement can be assured.

[Protective Layer: Effect]

With the configuration of the semiconductor device of the presentembodiment described above, since a protective layer surrounding ajoining electrode is formed, contact between water, which makes a factorof corrosion of the joining portion, and the joining electrode can besuppressed to the minimum. Therefore, corrosion of the joining electrodecan be suppressed, and a good electric characteristic and reliabilitycan be provided to the semiconductor device.

Accordingly, the semiconductor device improved in electriccharacteristic and reliability can be provided.

Further, since increase of the resistance value by corrosion can besuppressed, enhancement of the processing speed and reduction of powerconsumption of the semiconductor device can be anticipated.

Further, since the joining electrodes are surrounded by the protectivelayers, also external interference with an electric signal flowingthrough the electrode joining portion can be reduced. Accordingly,reduction in noise of the semiconductor device can be anticipated.

It is to be noted that the shape of the joining electrodes and theprotective layers is not limited to that described hereinabove inconnection with the present embodiment. The shape of the protectivelayers is not limited to the circular shape shown in FIG. 40B but may beany other shape only if they have a continuous shape surrounding ajoining electrode on the joining face thereof with the joiningelectrodes. Also the shape of the joining electrodes is not limited to acircular shape as shown in FIG. 40B but may be any other shape.

3. Fabrication Method of the Semiconductor Device

Now, an example of a fabrication method of the semiconductor device ofthe present embodiment is described. It is to be noted that, in thefollowing description of the fabrication method, only a fabricationmethod of the semiconductor device relating to the joining portionbetween the first joining electrode 941 and the fourth joining electrode961 described hereinabove with reference to FIGS. 40A and 40B isdescribed while description of a fabrication method of the configurationof the other part of the semiconductor device is omitted. The joiningportion between the second joining electrode 942 and the fifth joiningelectrode 962, the joining portion between the third joining electrode943 and the sixth joining electrode 963, and so forth can be fabricatedsimilarly as in the fabrication method of the semiconductor devicerelating to the joining portion between the first joining electrode 941and the fourth joining electrode 961. Further, description of aproduction method of the semiconductor substrates, wiring line layers,other various transistors and various elements is omitted because theycan be produced by known methods.

Further, like elements to those of the semiconductor device of thepresent embodiment described hereinabove with reference to FIGS. 40A and40B are denoted by like reference symbols, and overlapping detaileddescription of them is omitted herein to avoid redundancy.

First, a third interlayer insulating layer 955 connected to a grounddevice and including a barrier metal layer 946A and a first wiring line946 is formed as shown in FIG. 41A. The third interlayer insulatinglayer 955 including the first wiring line 946 can be formed using adamascene process (refer to, for example, Japanese Patent Laid-Open No.2004-63859) which is applied to a popular fabrication method for asemiconductor device or a like technique. Then, a second intermediatelayer 954 of 10 to 100 nm thick is formed on the first wiring line 946and the third interlayer insulating layer 955.

Then, a second interlayer insulating layer 953 in the form of a SiO2layer, a SiOC layer or the like of 20 to 200 nm thick is formed on thesecond intermediate layer 954 as seen in FIG. 41B. Then, a firstintermediate layer 952 in the form of a SiN layer, a SiCN layer or thelike of 10 to 100 nm thick is formed on the second interlayer insulatinglayer 953. A first interlayer insulating layer 951 in the form of a SiO2layer or a SiOC layer of 20 to 200 nm thick is formed on the firstintermediate layer 952.

The first interlayer insulating layer 951, first intermediate layer 952,second interlayer insulating layer 953, second intermediate layer 954and third interlayer insulating layer 955 described above can be formedusing, for example, a CVD method or a spin coating method.

Further, a resist layer 991 is formed on the first interlayer insulatinglayer 951 as shown in FIG. 41B. The resist layer 991 is formed in apattern in which it is open at a formation position thereof for a firstvia 956 and so forth for connection of a lower layer wiring linestructure such as the first wiring line 946.

Then, the first interlayer insulating layer 951, first intermediatelayer 952 and second interlayer insulating layer 953 are etched fromabove the resist layer 991 as seen in FIG. 41C by a dry etching methodusing a popular etching apparatus of the magnetron type.

After the first interlayer insulating layer 951, first intermediatelayer 952 and second interlayer insulating layer 953 are etched, forexample, an ashing process based on oxygen (O2) plasma and a process bysolution of organic amine-based drug are carried out. By the processes,the resist layer 991 and residual deposits generated in the etchingprocess are removed fully.

Then, an organic resin of 50 nm to 1 μm thick is applied by a spincoating method as shown in FIG. 41D and is calcined at 30 to 200° C. bya heater provided in an application apparatus to form an organicmaterial layer 992. Then, a SiO2 layer of 20 to 200 nm thick is formedon the organic material layer 992 by a CVD method or a spin coatingmethod to form an oxide layer 993.

Thereafter, a resist layer 994 is formed on the oxide layer 993 as shownin FIG. 41E. The resist layer 994 is formed in a pattern in which it isopen at a position at which the first joining electrode 941 of thejoining portion and the first protective layer 944 are to be formed.

Then, the oxide layer 993 is etched from above the resist layer 994 by adry etching method using a popular etching apparatus of the magnetrontype. Then, the etched oxide layer 993 is used to etch the organicmaterial layer 992 and the first interlayer insulating layer 951 by adry etching method using a popular etching apparatus of the magnetrontype.

Thereafter, an ashing process based on oxygen (O2) plasma and a processby solution of organic amine-based drug are carried out to fully removethe oxide layer 993, organic material layer 992 and residual depositsgenerated in the etching process. Further, by this process, the secondintermediate layer 954 on the first wiring line 946 is etchedsimultaneously to expose the first wiring line 946 to obtain such ashape as shown in FIG. 41G.

Then, a barrier material layer 995 for forming a barrier metal layer956A and the first protective layer 944 is formed as shown in FIG. 41H.The barrier material layer 995 is formed with a thickness of 5 to 50 nmfrom Ti, Ta, Ru or any of nitrides of them in an Ar/N2 atmosphere by anRF sputtering process.

Then, an electrode material layer 996 made of Cu or the like is formedon the barrier material layer 995 as shown in FIG. 41I using anelectrolytic plating method or a sputtering method. The electrodematerial layer 996 is formed so as to fill up the openings formed in thefirst interlayer insulating layer 951, first intermediate layer 952,second interlayer insulating layer 953 and second intermediate layer954. After the formation of the electrode material layer 996, a hotplate or a sinter annealing apparatus is used to carry out heattreatment at 100 to 400° C. for approximately one to 60 minutes.

Then, part of the deposited barrier material layer 995 and electrodematerial layer 996 which is unnecessary for wiring patterns is removedby a chemical mechanical polishing (CMP) method as shown in FIG. 41J. Bythis step, a first joining electrode 941 connecting to the first wiringline 946 through the first via 956 is formed. Simultaneously, a barriermetal layer 941A and a barrier metal layer 956A are formed.

Further, a first protective layer 944 is formed from the barriermaterial layer 995 remaining in the opening of the first interlayerinsulating layer 951.

A first joining portion 940 is formed by the steps described above.

Further, steps similar to those of the method described hereinabove withreference to FIGS. 41A to 41J are repeated to prepare a semiconductordevice having a second joining portion 960.

Then, for example, a Wet process using formic acid or a Dry processusing plasma of Ar, NH3, H2 or the like is carried out for the surfaceof the two semiconductor substrates formed by the process describedabove, that is, for the surface of the first joining portion 940 and thesecond joining portion 960. By the process, an oxide film on the surfaceof the first joining electrode 941 and the fourth joining electrode 961is removed to expose clean metal faces.

Then, after the surfaces of the two semiconductor substrates are opposedto each other, they are brought into contact with each other to join thefirst joining portion 940 and the second joining portion 960 to eachother as seen in FIG. 41K.

Thereupon, heat treatment is carried out at 100 to 400° C. forapproximately five minutes to two hours, for example, in an N2atmosphere of the atmospheric pressure or in vacuum by an annealingapparatus such as a hot plate or a RTA.

Further, upon the joining of the first joining portion 940 and thesecond joining portion 960 described above, a plasma joining method maybe used to join the first interlayer insulating layer 951 and the fourthinterlayer insulating layer 971 to each other. For example, oxygenplasma is irradiated upon the surface of the first interlayer insulatinglayer 951 and the fourth interlayer insulating layer 971 to modify thesurface of them. After the modification, the surfaces of the firstinterlayer insulating layer 951 and the fourth interlayer insulatinglayer 971 are washed for 30 seconds with pure water to form silanolgroups (Si—OH groups) on the surface. Then, the faces on which silanolgroups are formed are opposed to each other and partly pressed againsteach other so as to be joined together by Van der Waals force.Thereafter, in order to further increase the close contacting force atthe joining interface, heat treatment of, for example, 400° C./60 min isapplied to cause a dehydration condensation reaction of the silanolgroups.

By the steps described above, a semiconductor device of the presentembodiment shown in FIG. 41K can be fabricated.

By the fabrication method described above, the barrier metal layer 956Aand the first protective layer 944 can be formed at the same time.Further, the recessed portion of the first interlayer insulating layer951 for forming the first protective layer 944 can be formedsimultaneously with the recessed portion for forming the first joiningelectrode 941.

Therefore, the semiconductor device of the present embodiment can befabricated by a popular fabrication method for a semiconductor devicewithout adding a step for forming a protective layer.

An example of a size of the components of the semiconductor device shownin FIG. 41K is given below.

The opening diameter of the first via 956 and the fourth via 976connecting to the first wiring line 946 and the fourth wiring line 966,respectively, is 50 to 200 nm. The opening diameter of the first joiningelectrode 941 and the fourth joining electrode 961 is 200 nm to 20 μm.The opening width of the first protective layer 944 and the thirdprotective layer 964 formed around the first joining electrode 941 andthe fourth joining electrode 961 and surrounding the joining portions,respectively, is 10 nm to 20 μm.

4. Modification 1 to the Semiconductor Device

Now, a modification 1 to the semiconductor device of the presentembodiment is described. FIGS. 42A and 42B show a configuration of thesemiconductor device of the modification 1. It is to be noted that, inthe semiconductor device shown in FIGS. 42A and 42B, like elements tothose of the semiconductor device of the embodiment describedhereinabove are denoted by like reference characters, and overlappingdetailed description of them is omitted herein to avoid redundancy.Further, the semiconductor device of the modification 1 shown in FIGS.42A and 42B is similar in configuration to the semiconductor device ofthe embodiment described above except the configuration of the otherpart than protective layers. Therefore, description of the configurationof the components other than the protective layers is omitted herein toavoid redundancy.

[Protective Layer]

Referring first to FIG. 42A, the first joining portion 940 includes afirst protective layer 981 around the first joining electrode 941. Thefirst joining portion 940 further includes a second protective layer 982surrounding the second joining electrode 942 and the third joiningelectrode 943.

Referring to FIG. 42B, the first protective layer 981 is formed from asingle continuous layer surrounding the first joining electrode 941. Thesecond protective layer 982 is formed from a single continuous layersurrounding the second joining electrode 942 and third joining electrode943.

Referring back to FIG. 42A, the first protective layer 981 includes abarrier metal layer 981B which covers the inner face of a recessedportion formed in the first interlayer insulating layer 951, and aconductor layer 981A formed so as to fill up the barrier metal layer981B.

The first protective layer 981 is formed with such a depth that itextends from the joining face 950 of the first joining portion 940through the first interlayer insulating layer 951 to the firstintermediate layer 952.

Meanwhile, the second protective layer 982 includes a barrier metallayer 982B which covers the inner face of a recessed portion formed inthe first interlayer insulating layer 951, first intermediate layer 952and second interlayer insulating layer 953, and a conductor layer 982Aformed so as to fill up the barrier metal layer 982B. The secondprotective layer 982 is formed with such a depth that it extends fromthe joining face 950 of the first joining portion 940 through the firstinterlayer insulating layer 951, first intermediate layer 952 and secondinterlayer insulating layer 953 to the second intermediate layer 954.

Further, as seen in FIG. 42A, a third protective layer 964 is providedat a position on the second joining portion 960 corresponding to thefirst protective layer 981 described hereinabove. Further, a fourthprotective layer 965 is provided at a position of the second joiningportion 960 corresponding to the second protective layer 982. The thirdand fourth protective layers 964 and 965 have a configuration similar tothat in the embodiment described hereinabove with reference to FIGS. 40Aand 40B.

On the joining face 950, the first protective layer 981 and the thirdprotective layer 964 are provided at positions at which they contactwith each other. Further, on the joining face 950, the second protectivelayer 982 and the fourth protective layer 965 are provided at positionsat which they contact with each other.

By the configuration just described, a joining portion between the firstjoining electrode 941 and the fourth joining electrode 961 is formed ina region surrounded by the first protective layer 981, third protectivelayer 964, first intermediate layer 952 and third intermediate layer972. Meanwhile, a joining portion between the second joining electrode942 and the fifth joining electrode 962 and a joining portion betweenthe third joining electrode 943 and the sixth joining electrode 963 areformed in a region surrounded by the second protective layer 982, fourthprotective layer 965, second intermediate layer 954 and thirdintermediate layer 972.

The barrier metal layers 981B and 982B of the first and secondprotective layers 981 and 982 are formed from a material similar to thatof the barrier metal layers described hereinabove, such as Ta, Ti, Ru,TaN or TiN. Further, the conductor layers 981A and 982A of the first andsecond protective layers 981 and 982 are formed from a material similarto that of the joining electrodes described hereinabove such as, forexample, Cu.

[Protective Layer: Effect]

With the configuration of the semiconductor device of the modification 1shown in FIG. 42A, the width of the joining face between the firstprotective layer 981 and the second protective layer 982 is set greaterthan the width of the third protective layer 964 and the fourthprotective layer 965 to assure connection reliability against positionaldisplacement.

The configuration of the first protective layer 981 and the secondprotective layer 982 is suitable, for example, where the width of one ofthe protective layers to be joined to each other is made greater thanthat of the other protective layer in order to assure connectionreliability of the protective layers. For example, in the case where theopening diameter or width of the first protective layer 981 isapproximately 30 nm to 20 μm, it is difficult to fill up the openingformed in the insulating layers only by filling with the barrier metallayers 981B and 982B. Therefore, by filling up the barrier metal layers981B and 982B with the conductor layers 981A and 982A after the innerface of the opening is covered with the barrier metal layers 981B and982B, the first protective layer 981 and the second protective layer 982having a large width of the joining face therebetween can be configured.

5. Fabrication Method for the Modification 1 to the Semiconductor Device

Now, a fabrication method for the semiconductor device of themodification 1 described above is described. In the followingdescription of the fabrication method, only a fabrication method of thesemiconductor device relating to the joining portion between the firstjoining electrode 941 and the fourth joining electrode 961 describedhereinabove with reference to FIGS. 42A and 42B is described while afabrication method of the configuration of the other part of thesemiconductor device is omitted.

First, steps similar to those at the steps described hereinabove withreference to FIGS. 41A to 41D are carried out to form a secondintermediate layer 954, a second interlayer insulating layer 953, afirst intermediate layer 952, a first interlayer insulating layer 951,an organic material layer 992 and an oxide layer 993 on a thirdinterlayer insulating layer 955 on which a first wiring line 946 isformed. The second interlayer insulating layer 953, first intermediatelayer 952 and first interlayer insulating layer 951 have an opening forforming a first via 956 therein.

Then, a resist layer 997 is formed on the oxide layer 993 as shown inFIG. 43A. The resist layer 997 is formed in a pattern which is open atpositions at which a first joining electrode 941 and a first protectivelayer 981 of a joining portion are to be formed.

Then, the oxide layer 993 is etched from above the resist layer 997 asseen in FIG. 43B by a dry etching method in which a popular etchingapparatus of the magnetron type is used. Then, the etched oxide layer993 is used as a mask to etch the organic material layer 992 and thefirst interlayer insulating layer 951 by a dry etching method in which apopular etching apparatus of the magnetron type is used.

Thereafter, for example, an ashing process based on oxygen (O2) plasmaand a process by solution of organic amine-based drug are carried out tofully remove the oxide layer 993, organic material layer 992 andresidual deposits generated in the etching process. Further, by thisprocess, the second intermediate layer 954 on the first wiring line 946is etched simultaneously to expose the first wiring line 946 thereby toobtain such a shape as shown in FIG. 43C.

Then, a barrier material layer 998 for forming the barrier metal layer956A and the barrier metal layer 981B of the first protective layer 981is formed as shown in FIG. 43D. The barrier material layer 998 is formedwith a thickness of 5 to 50 nm from Ti, Ta, Ru or any of nitrides ofthem in an Ar/N2 atmosphere by an RF sputtering process.

Then, an electrode material layer 999 made of Cu or the like is formedon the barrier material layer 998 as seen in FIG. 43E using anelectrolytic plating method or a sputtering method. The electrodematerial layer 999 is formed by filling up an opening in which the firstjoining electrode 941 is to be formed and an opening in which the firstprotective layer 981 is to be formed. After the formation of theelectrode material layer 999, a hot plate or a sinter annealingapparatus is used to carry out heat treatment at 100 to 400° C. forapproximately one to 60 minutes.

Then, part of the barrier material layer 998 and the electrode materiallayer 999 which is unnecessary for wiring line patterns is removed asseen in FIG. 43F by a chemical mechanical polishing (CMP) method. Bythis process, a first joining electrode 941 which connects to the firstwiring line 946 through the first via 956 is formed. Simultaneously, abarrier metal layer 941A and a barrier metal layer 956A are formed.

Further, a first protective layer 981 is formed from the barriermaterial layer 998 and the electrode material layer 999 remaining in theopening of the first interlayer insulating layer 951.

By the steps described above, a first joining portion 940 is formed.

Steps similar to those of the method described hereinabove withreference to FIGS. 41A to 41J are repeated to prepare a semiconductordevice having a second joining portion 960.

Then, for example, a wet etching process using forming acid or a dryetching process using plasma of Ar, NH3, H2 or the like is carried outfor the surface of the two semiconductor members formed by the processdescribed above, that is, for the surface of the first joining portion940 and the second joining portion 960. By the process, an oxide film onthe surface of the first joining electrode 941 and the fourth joiningelectrode 961 is removed to expose clean metal faces.

Then, after the surfaces of the two semiconductor members are opposed toeach other, they are brought into contact with each other to join thefirst joining portion 940 and the second joining portion 960 to eachother as seen in FIG. 43G.

Thereupon, heat treatment is carried out at 100 to 400° C. forapproximately five minutes to two hours, for example, in an N2atmosphere of the atmospheric pressure or in vacuum by an annealingapparatus such as a hot plate or a RTA.

By the steps described above, a semiconductor device of the presentmodification shown in FIG. 43G can be fabricated.

6. Modification 2 to the Semiconductor Device

Now, a modification 2 to the semiconductor device of the presentembodiment is described. FIG. 44 shows a configuration of thesemiconductor device of the modification 2. It is to be noted that, inthe semiconductor device shown in FIG. 44, like elements to those of thesemiconductor device of the embodiment described hereinabove are denotedby like reference characters, and overlapping detailed description ofthem is omitted herein to avoid redundancy. Further, the semiconductordevice of the modification 2 shown in FIG. 44 is similar inconfiguration to the semiconductor device of the embodiment describedabove except the configuration of the other part than interlayerinsulating layers. Therefore, description of the configuration of thecomponents other than the interlayer insulating layers is omitted hereinto avoid redundancy.

[Insulating Layer]

The first joining portion 940 and the second joining portion 960 areformed by lamination of a plurality of wiring line layers and insulatinglayers.

The insulating layers of the first joining portion 940 include a firstinterlayer insulating layer 983 and a second interlayer insulating layer984 in order from the joining face 950 side. Meanwhile, the insulatinglayers of the second joining portion 960 include a third interlayerinsulating layer 985 and a fourth interlayer insulating layer 986 inorder from the joining face 950.

In the first joining portion 940, a first wiring line 946, a secondwiring line 947 and a third wiring line 948 are formed in the secondinterlayer insulating layer 984. In the first interlayer insulatinglayer 983, a first joining electrode 941, a second joining electrode 942and a third joining electrode 943 of the first joining portion 940 areformed. The surface of the first, second and third joining electrodes941, 942 and 943 is exposed to the joining face 950 and lies in flushwith the first interlayer insulating layer 983.

Further, a first via 956, a second via 957 and a third via 958 areformed in the first interlayer insulating layer 983.

Furthermore, a first protective layer 944 which surrounds the firstjoining electrode 941 and a second protective layer 945 which surroundsthe second joining electrode 942 and the third joining electrode 943 areprovided in the first interlayer insulating layer 983.

In the second joining portion 960, a fourth wiring line 966, a fifthwiring line 967 and a sixth wiring line 968 are formed in the fourthinterlayer insulating layer 986. A fourth joining electrode 961, a fifthjoining electrode 962 and a sixth joining electrode 963 are formed inthe third interlayer insulating layer 985. The surface of the fourthjoining electrode 961, fifth joining electrode 962 and sixth joiningelectrode 963 is exposed to the joining face 950 and lies in flush withthe third interlayer insulating layer 985.

Further, a fourth via 976, a fifth via 977 and a sixth via 978 areformed in the third interlayer insulating layer 985.

Furthermore, a third protective layer 964 which surrounds the fourthjoining electrode 961 and a fourth protective layer 965 which surroundsthe fifth joining electrode 962 and the sixth joining electrode 963 areprovided in the third interlayer insulating layer 985.

The first interlayer insulating layer 983 and the third interlayerinsulating layer 985 are configured from a material same as that of theintermediate layers of the semiconductor device of the embodimentdescribed hereinabove. For example, the first interlayer insulatinglayer 983 and the third interlayer insulating layer 985 are configuredfrom a material used for a diffusion preventing layer of a metalmaterial which popularly configures wiring lines and so forth in asemiconductor device. Further, the first interlayer insulating layer 983and the third interlayer insulating layer 985 are high densityinsulating layers which are less likely to allow water 970 included inthe interlayer insulating layers to penetrate therethrough. Further,such high density insulating layers serving as diffusion preventinglayers as just described are configured from P—SiN of a relativedielectric constant of 4 to 7 formed, for example, by a spin coatingmethod or a CVD method or from SiCN or the like of a relative dielectricconstant lower than 4 in which C is contained.

Further, the second interlayer insulating layer 984 and the fourthinterlayer insulating layer 986 are configured from a material same asthat of the interlayer insulating layers of the semiconductor device ofthe embodiment described above. For example, the second interlayerinsulating layer 984 and the fourth interlayer insulating layer 986 areconfigured, for example, from SiO2, organic silicon-based polymerrepresented by fluorine-containing silicon oxide (FSG) or polyallylether (PAE), an inorganic material represented by hydrogensilsesquioxane(HSQ) or methylsilsesquioxane (MSQ), and particularly from alow-dielectric constant (low-k) material having a relative dielectricconstant of approximately 2.7 or lower.

In the configuration of the semiconductor device of the modification 2described above, the first interlayer insulating layer 983 and the thirdinterlayer insulating layer 985 which form the joining face 950 are lesslikely to allow water to penetrate therethrough. Therefore, at thejoining portion between the first joining electrode 941 and the fourthjoining electrode 961, contact of water 970 into the contacting portion969 between the fourth joining electrode 961 and the first interlayerinsulating layer 983 can be suppressed. Similarly, at the joiningportion between the second joining electrode 942 and the fifth joiningelectrode 962, contact of water 970 with the contacting portion 949between the second joining electrode 942 and the third interlayerinsulating layer 985 can be suppressed.

Further, since the first, second, third and fourth protective layers944, 945, 964 and 965 are provided, migration of water appearing on thejoining face upon plasma joining or water included in the interlayerinsulating layers to the electrode joining portions can be suppressed.Therefore, corrosion of the joining electrode can be suppressed, and agood electric characteristic and reliability can be provided to thesemiconductor device.

[Fabrication Method]

The semiconductor device of the modification 2 described hereinabovewith reference to FIG. 44 can be fabricated by changing the material ofthe interlayer insulating layers to be laminated and the etchingconditions of the interlayer insulating layers in the fabrication methodof the semiconductor device of the embodiment described hereinabove. Forexample, an interlayer insulating layer in the form of a single layer isformed at the steps of forming an interlayer insulating layer and anintermediate layer illustrated in FIGS. 41A and 41B. Then, at theetching step, the etching time is controlled to form a recessed portionto a desired depth of the interlayer insulating layer. By changing thefabrication process in this manner, the semiconductor device of themodification 2 can be fabricated by a method similar to that for thesemiconductor device of the embodiment described hereinabove.

7. Embodiment of the Electronic Apparatus

The semiconductor device of the embodiment described above can beapplied to an arbitrary electronic apparatus wherein two semiconductormembers are bonded to each other to carry out wiring line joining suchas, for example, a solid-state image pickup device, a semiconductormemory or a semiconductor logic device such as an IC.

Fifth Embodiment Example of an Electronic Apparatus which Uses any ofthe Semiconductor Devices of the Embodiments

Any of the semiconductor devices such as a solid-state image pickupdevice according to the present technology described hereinabove inconnection with the embodiments can be applied to various electronicapparatus such as, for example, a camera system such as a digital cameraor a video camera, a portable telephone set having an image pickupfunction or any other apparatus having an image pickup function.

FIG. 45 shows a configuration of a camera, in which a solid-state imagepickup device is used, as an example of the electronic apparatusaccording to the present technology. The camera according to the presentembodiment is applied as a video camera which can pick up a still imageor a dynamic image. Referring to FIG. 45, the camera 90 includes asolid-state image pickup device 91, an optical system 93 for introducingincident light thereto to a reception light sensor of the solid-stateimage pickup device 91, a shutter apparatus 94, a driving circuit 95 fordriving the solid-state image pickup device 91, and a signal processingcircuit 96 for processing an output signal of the solid-state imagepickup device 91.

The solid-state image pickup device 91 is configured by applying any ofthe semiconductor devices described hereinabove in connection with theembodiments and modifications of the disclosed technology. The opticalsystem 93 including an optical lens introduces image light, that is,incident light, from an image pickup object so as to form an image on animage pickup plane of the solid-state image pickup device 91.Consequently, signal charge is accumulated for a fixed period of timeinto the solid-state image pickup device 91. Such an optical system 93as described above may be an optical lens system configured from aplurality of optical lenses. The shutter apparatus 94 controls the lightirradiation time period and the light interception time period to thesolid-state image pickup device 91. The driving circuit 95 supplies adriving signal to the solid-state image pickup device 91 and the shutterapparatus 94 so that control of a signal outputting operation of thesolid-state image pickup device 91 to the signal processing circuit 96and a shutter operation of the shutter apparatus 94 is carried out inaccordance with the supplied driving signals or timing signals. Inparticular, the driving circuit 95 supplies a driving signal or timingsignal to carry out a signal transfer operation from the solid-stateimage pickup device 91 to the signal processing circuit 96. The signalprocessing circuit 96 carries out various signal processes for thesignal supplied thereto from the solid-state image pickup device 91. Avideo signal obtained by the signal processes is stored into a storagemedium such as a memory or outputted to a monitor.

It should be understood by those skilled in the art that variousmodifications, combinations, sub-combinations and alternations may occurdepending on design requirements and other factors insofar as they arewithin the scope of the appended claims or the equivalent thereof.

What is claimed is:
 1. A semiconductor device, comprising: a firstsubstrate having a bonding face to which a first electrode and a firstinsulating film are exposed; an insulating thin film configured to coverthe bonding face of said first substrate; and a second substrate havinga bonding face to which a second electrode and a second insulating filmare exposed and bonded to said first substrate in a state in which saidinsulating thin film is sandwiched between the bonding face of saidsecond substrate and the bonding face of said first substrate and saidfirst electrode and said second electrode are electrically connected toeach other through said insulating thin film.
 2. The semiconductordevice according to claim 1, wherein said insulating thin film is anoxide film.
 3. The semiconductor device according to claim 1, whereinsaid insulating thin film is a nitride film.
 4. The semiconductor deviceaccording to claim 1, wherein said insulating thin film has a laminationstructure.
 5. The semiconductor device according to claim 1, whereinsaid insulating thin film is provided in a state in which saidinsulating thin film covers an overall area of each of the bondingfaces.
 6. The semiconductor device according to claim 1, wherein thebonding face of said first substrate and the bonding face of said secondsubstrate are flattened faces.
 7. A fabrication method for asemiconductor device, comprising: preparing two substrates each having abonding face to which an electrode and an insulating film are exposed;forming an insulating thin film in a state in which the insulating thinfilm covers the bonding face of at least one of the two substrates; anddisposing the two substrates such that the bonding faces thereof areopposed to each other across the insulating thin film, positioning thetwo substrates in a state in which the electrodes thereof areelectrically connected to each other through the insulating thin filmand bonding the two substrates in the positioned state.
 8. Thefabrication method for a semiconductor device according to claim 7,wherein the insulating thin film is formed on both of the twosubstrates.
 9. The fabrication method for a semiconductor deviceaccording to claim 7, wherein the insulating thin film of a samematerial is formed on both of the two substrates.
 10. The fabricationmethod for a semiconductor device according to claim 7, wherein theinsulating thin film is formed by an atomic layer deposition method. 11.The fabrication method for a semiconductor device according to claim 7,wherein the bonding faces of the two substrates are formed by aflattening process.
 12. A camera system comprising: a solid-state imagepickup device; an optical system that forms a subject image on thesolid-state imaging device; and a signal processing circuit thatprocesses an output image signal of the solid-state imaging device,wherein the solid-state image pickup device includes: a first substratehaving a bonding face to which a first electrode and a first insulatingfilm are exposed; an insulating thin film configured to cover thebonding face of said first substrate; and a second substrate having abonding face to which a second electrode and a second insulating filmare exposed and bonded to said first substrate in a state in which saidinsulating thin film is sandwiched between the bonding face of saidsecond substrate and the bonding face of said first substrate and saidfirst electrode and said second electrode are electrically connected toeach other through said insulating thin film.
 13. The camera systemaccording to claim 12, wherein said insulating thin film is an oxidefilm.
 14. The camera system according to claim 12, wherein saidinsulating thin film is a nitride film.
 15. The camera system accordingto claim 12, wherein said insulating thin film has a laminationstructure.
 16. The camera system according to claim 12, wherein saidinsulating thin film is provided in a state in which said insulatingthin film covers an overall area of each of the bonding faces.
 17. Thecamera system according to claim 12, wherein the bonding face of saidfirst substrate and the bonding face of said second substrate areflattened faces.